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ORACLE Tutorials

COLLECTIONS AND RECORDS in PL/SQL

-- Source Oracle Documentation
Many programming techniques use collection types such as arrays, bags, lists, nested tables, sets, and trees. To support these techniques in database applications, PL/SQL provides the datatypes TABLE and VARRAY, which allow you to declare index-by tables, nested tables and variable-size arrays. In this chapter, you learn how those types let you reference and manipulate collections of data as whole objects. You also learn how the datatype RECORD lets you treat related but dissimilar data as a logical unit.

There are three types of collections.

VARRAYs

For varrays, use the syntax:

TYPE type_name IS {VARRAY | VARYING ARRAY} (size_limit)
OF element_type [NOT NULL];


The meanings of type_name and element_type are the same as for nested tables also.

SIZE_LIMIT is a positive integer literal representing the maximum number of elements in the array. When defining a VARRAY type, you must specify its maximum size. In the following example, you define a type that stores up to 366 dates:

DECLARE
TYPE CalYear IS VARRAY (366) OF DATE;

Nested Tables

For nested tables, use the syntax:

TYPE type_name IS TABLE OF element_type [NOT NULL];

type_name is a type specifier used later to declare collections. For nested tables declared within PL/SQL, element_type is any PL/SQL datatype except:

REF CURSOR

Nested tables declared globally in SQL have additional restrictions on the element type. They cannot use the following element types:

BINARY_INTEGER, PLS_INTEGER
BOOLEAN
LONG, LONG RAW
NATURAL, NATURALN
POSITIVE, POSITIVEN
REF CURSOR
SIGNTYPE
STRING

Associative Arrays

For associative arrays (also known as index-by tables), use the syntax:

TYPE type_name IS TABLE OF element_type [NOT NULL]
INDEX BY [BINARY_INTEGER | PLS_INTEGER | VARCHAR2 (size_limit)];
INDEX BY key_type;


The key_type can be numeric, either BINARY_INTEGER or PLS_INTEGER. It can also be VARCHAR2 or one of its subtypes VARCHAR, STRING, or LONG. You must specify the length of a VARCHAR2-based key, except for LONG which is equivalent to declaring a key type of VARCHAR2 (32760). The types RAW, LONG RAW, ROWID, CHAR, and CHARACTER are not allowed as keys for an associative array.
An initialization clause is not required (or allowed).

When you reference an element of an associative array that uses a VARCHAR2-based key, you can use other types, such as DATE or TIMESTAMP, as long as they can be converted to VARCHAR2 with the TO_CHAR function.

Index-by tables can store data using a primary key value as the index, where the key values are not sequential. In the example below, you store a single record in the index-by table, and its subscript is 7468 rather than 1.

DECLARE

TYPE EmpTabTyp IS TABLE OF emp%ROWTYPE
INDEX BY BINARY_INTEGER;
emp_tab EmpTabTyp;

BEGIN

/* Retrieve employee record. */
SELECT * INTO emp_tab (7468) FROM emp WHERE empno = 7468;

END;

Declaring PL/SQL Collection Variables

Once you define a collection type, you can declare variables of that type. You use the new type name in the declaration, the same as with predefined types such as NUMBER and INTEGER.

Example: Declaring Nested Tables, Varrays, and Associative Arrays

DECLARE
TYPE nested_type IS TABLE OF VARCHAR2 (20);
TYPE varray_type IS VARRAY (50) OF INTEGER;
TYPE associative_array_type IS TABLE OF NUMBER
INDEXED BY BINARY_INTEGER;
v1 nested_type;
v2 varray_type;
v3 associative_array_type;


%TYPE Example

You can use %TYPE to specify the datatype of a previously declared collection, so that changing the definition of the collection automatically updates other variables that depend on the number of elements or the element type:

DECLARE
TYPE Platoon IS VARRAY (20) OF Soldier;
p1 Platoon;
-- If we change the number of soldiers in a platoon, p2 will
-- reflect that change when this block is recompiled.
p2 p1%TYPE;


Example: Declaring a Procedure Parameter as a Nested Table

You can declare collections as the formal parameters of functions and procedures. That way, you can pass collections to stored subprograms and from one subprogram to another. The following example declares a nested table as a parameter of a packaged procedure:

CREATE PACKAGE personnel AS
TYPE Staff IS TABLE OF Employee;
...
PROCEDURE award_bonuses (members IN Staff);
END personnel;


To call PERSONNEL.AWARD_BONUSES from outside the package, you declare a variable of type PERSONNEL.STAFF and pass that variable as the parameter.

You can also specify a collection type in the RETURN clause of a function specification:

DECLARE
TYPE SalesForce IS VARRAY (25) OF Salesperson;
FUNCTION top_performers (n INTEGER) RETURN SalesForce IS ...


Example: Specifying Collection Element Types with %TYPE and %ROWTYPE

To specify the element type, you can use %TYPE, which provides the datatype of a variable or database column. Also, you can use %ROWTYPE, which provides the rowtype of a cursor or database table. Two examples follow:

DECLARE

TYPE EmpList IS TABLE OF emp.ename%TYPE; -- based on column
CURSOR c1 IS SELECT * FROM dept;
TYPE DeptFile IS VARRAY (20) OF c1%ROWTYPE; -- based on cursor


Example: VARRAY of Records

In the next example, you use a RECORD type to specify the element type:

DECLARE
TYPE AnEntry IS RECORD (
term VARCHAR2 (20),
meaning VARCHAR2 (200));
TYPE Glossary IS VARRAY (250) OF AnEntry;


Example: NOT NULL Constraint on Collection Elements
You can also impose a NOT NULL constraint on the element type:

DECLARE
TYPE EmpList IS TABLE OF emp.empno%TYPE NOT NULL;


Initializing and Referencing Collections

Until you initialize it, a nested table or varray is atomically null: the collection itself is null, not its elements. To initialize a nested table or varray, you use a constructor, a system-defined function with the same name as the collection type. This function "constructs" collections from the elements passed to it.

You must explicitly call a constructor for each varray and nested table variable. (Associative arrays, the third kind of collection, do not use constructors.) Constructor calls are allowed wherever function calls are allowed.

Example: Constructor for a Nested Table

In the following example, you pass multiple elements to the constructor CourseList (), which returns a nested table containing those elements:

DECLARE
TYPE CourseList IS TABLE OF VARCHAR2(16);
my_courses CourseList;
BEGIN
my_courses :=
CourseList('Econ 2010', 'Acct 3401', 'Mgmt 3100');
END;


Because a nested table does not have a declared maximum size, you can put as many elements in the constructor as necessary.

Example: Constructor for a Varray

In the next example, you pass three objects to constructor ProjectList(), which returns a varray containing those objects:

DECLARE
TYPE ProjectList IS VARRAY(50) OF VARCHAR2(16);
accounting_projects ProjectList;
BEGIN
accounting_projects :=
ProjectList('Expense Report', 'Outsourcing', 'Auditing');
END;

You need not initialize the whole varray. For example, if a varray has a maximum size of 50, you can pass fewer than 50 elements to its constructor.

Example: Collection Constructor Including Null Elements

Unless you impose the NOT NULL constraint, you can pass null elements to a constructor. An example follows:

BEGIN
my_courses := CourseList('Math 3010', NULL, 'Stat 3202');


Example: Combining Collection Declaration and Constructor
You can initialize a collection in its declaration, which is a good programming practice:

DECLARE
TYPE CourseList IS TABLE OF VARCHAR2(16);
my_courses CourseList :=
CourseList('Art 1111', 'Hist 3100', 'Engl 2005');


Example: Empty Varray Constructor
If you call a constructor without arguments, you get an empty but non-null collection:

DECLARE
TYPE Clientele IS VARRAY(100) OF Customer;
vips Clientele := Clientele(); -- initialize empty varray
BEGIN
IF vips IS NOT NULL THEN -- condition yields TRUE
...
END IF;
END;


In this case, you can call the collection's EXTEND method to add elements later.

Example: Nested Table Constructor Within a SQL Statement
In this example, you insert several scalar values and a CourseList nested table into the SOPHOMORES table.

BEGIN
INSERT INTO sophomores
VALUES (5035, 'Janet Alvarez', '122 Broad St', 'FT',
CourseList('Econ 2010', 'Acct 3401', 'Mgmt 3100'));


Example: Varray Constructor Within a SQL Statement
In this example, you insert a row into database table DEPARTMENT. The varray constructor ProjectList() provides a value for column PROJECTS.

BEGIN
INSERT INTO department
VALUES(60, 'Security', 750400,
ProjectList('New Badges', 'Track Computers', 'Check Exits'));


Example: Datatype Compatibility
This example shows that collections must have the same datatype for an assignment to work. Having the same element type is not enough.

DECLARE
TYPE Clientele IS VARRAY(100) OF Customer;
TYPE Vips IS VARRAY(100) OF Customer;
-- These first two variables have the same datatype.
group1 Clientele := Clientele(...);
group2 Clientele := Clientele(...);
-- This third variable has a similar declaration,
-- but is not the same type.
group3 Vips := Vips(...);
BEGIN
-- Allowed because they have the same datatype
group2 := group1;
-- Not allowed because they have different datatypes
group3 := group2;
END;


Example: Assigning a Null Value to a Nested Table
You assign an atomically null nested table or varray to a second nested table or varray. In this case, the second collection must be reinitialized:

DECLARE
TYPE Clientele IS TABLE OF VARCHAR2 (64);
-- This nested table has some values.
group1 Clientele: = Clientele ('Customer 1','Customer 2');
-- This nested table is not initialized ("atomically null").
group2 Clientele;
BEGIN
-- At first, the test IF group1 IS NULL yields FALSE.
-- Then we assign a null nested table to group1.
group1:= group2;
-- Now the test IF group1 IS NULL yields TRUE.
-- We must use another constructor to give it some values.
END;


In the same way, assigning the value NULL to a collection makes it atomically null.

Example: Possible Exceptions for Collection Assignments
Assigning a value to a collection element can cause various exceptions:

If the subscript is null or is not convertible to the right datatype, PL/SQL raises the predefined exception VALUE_ERROR. Usually, the subscript must be an integer. Associative arrays can also be declared to have VARCHAR2 subscripts.
If the subscript refers to an uninitialized element, PL/SQL raises SUBSCRIPT_BEYOND_COUNT.
If the collection is atomically null, PL/SQL raises COLLECTION_IS_NULL.
DECLARE
TYPE WordList IS TABLE OF VARCHAR2 (5);
words WordList;
BEGIN
/* Assume execution continues despite the raised exceptions. */
-- Raises COLLECTION_IS_NULL. We haven't used a constructor yet.
-- This exception applies to varrays and nested tables, but not
-- associative arrays which don't need a constructor.
words (1):= 10;
-- After using a constructor, we can assign values to the elements.
words: = WordList (10, 20, 30);
-- Any expression that returns a VARCHAR2 (5) is OK.
words (1):= 'yes';
words (2):= words (1) || 'no';
-- Raises VALUE_ERROR because the assigned value is too long.
words (3):= 'longer than 5 characters';
-- Raises VALUE_ERROR because the subscript of a nested table must
-- be an integer.
words ('B'):= 'dunno';
-- Raises SUBSCRIPT_BEYOND_COUNT because we only made 3 elements
-- in the constructor. To add new ones, we must call the EXTEND
-- method first.
words (4):= 'maybe';
END;

Manipulating Individual Collection Elements with SQL
By default, SQL operations store and retrieve whole collections rather than individual elements. To manipulate the individual elements of a collection with SQL, use the TABLE operator. The TABLE operator uses a subquery to extract the varray or nested table, so that the INSERT, UPDATE, or DELETE statement applies to the nested table rather than the top-level table.

Example: Inserting an Element into a Nested Table with SQL
In the following example, you add a row to the History Department nested table stored in column COURSES:

BEGIN
-- The TABLE operator makes the statement apply to the nested
-- table from the 'History' row of the DEPARTMENT table.
INSERT INTO
TABLE(SELECT courses FROM department WHERE name = 'History')
VALUES('Modern China');
END;


Example: Updating Elements Inside a Nested Table with SQL
In the next example, you abbreviate the names for some courses offered by the Psychology Department:


BEGIN
UPDATE TABLE(SELECT courses FROM department
WHERE name = 'Psychology')
SET credits = credits + adjustment
WHERE course_no IN (2200, 3540);
END;


Example: Retrieving a Single Element from a Nested Table with SQL
In the following example, you retrieve the title of a specific course offered by the History Department:

DECLARE
my_title VARCHAR2(64);
BEGIN
-- We know that there is one history course with 'Etruscan'
-- in the title. This query retrieves the complete title
-- from the nested table of courses for the History department.
SELECT title INTO my_title
FROM
TABLE(SELECT courses FROM department WHERE name = 'History')
WHERE name LIKE '%Etruscan%';
END;


Example: Deleting Elements from a Nested Table with SQL
In the next example, you delete all 5-credit courses offered by the English Department:

BEGIN
DELETE TABLE(SELECT courses FROM department
WHERE name = 'English')
WHERE credits = 5;
END;


Example: Retrieving Elements from a Varray with SQL
In the following example, you retrieve the title and cost of the Maintenance Department's fourth project from the varray column projects:

DECLARE
my_cost NUMBER(7,2);
my_title VARCHAR2(35);
BEGIN
SELECT cost, title INTO my_cost, my_title
FROM TABLE(SELECT projects FROM department
WHERE dept_id = 50)
WHERE project_no = 4;
...
END;


Example: Performing INSERT, UPDATE, and DELETE Operations on a Varray with SQL
Currently, you cannot reference the individual elements of a varray in an INSERT, UPDATE, or DELETE statement. You must retrieve the entire varray, use PL/SQL procedural statements to add, delete, or update its elements, and then store the changed varray back in the database table.

In the following example, stored procedure ADD_PROJECT inserts a new project into a department's project list at a given position:

CREATE PROCEDURE add_project (
dept_no IN NUMBER,
new_project IN Project,
position IN NUMBER) AS
my_projects ProjectList;
BEGIN
SELECT projects INTO my_projects FROM department
WHERE dept_no = dept_id FOR UPDATE OF projects;
my_projects.EXTEND; -- make room for new project
/* Move varray elements forward. */
FOR i IN REVERSE position..my_projects.LAST - 1 LOOP
my_projects(i + 1) := my_projects(i);
END LOOP;
my_projects(position) := new_project; -- add new project
UPDATE department SET projects = my_projects
WHERE dept_no = dept_id;
END add_project;


The following stored procedure updates a given project:

CREATE PROCEDURE update_project (
dept_no IN NUMBER,
proj_no IN NUMBER,
new_title IN VARCHAR2 DEFAULT NULL,
new_cost IN NUMBER DEFAULT NULL) AS
my_projects ProjectList;
BEGIN
SELECT projects INTO my_projects FROM department
WHERE dept_no = dept_id FOR UPDATE OF projects;
/* Find project, update it, then exit loop immediately. */
FOR i IN my_projects.FIRST..my_projects.LAST LOOP
IF my_projects(i).project_no = proj_no THEN
IF new_title IS NOT NULL THEN
my_projects(i).title := new_title;
END IF;
IF new_cost IS NOT NULL THEN
my_projects(i).cost := new_cost;
END IF;
EXIT;
END IF;
END LOOP;
UPDATE department SET projects = my_projects
WHERE dept_no = dept_id;
END update_project;

Example: Performing INSERT, UPDATE, and DELETE Operations on PL/SQL Nested Tables
To perform DML operations on a PL/SQL nested table, use the operators TABLE and CAST. This way, you can do set operations on nested tables using SQL notation, without actually storing the nested tables in the database.

The operands of CAST are PL/SQL collection variable and a SQL collection type (created by the CREATE TYPE statement). CAST converts the PL/SQL collection to the SQL type.

The following example counts the number of differences between a revised course list and the original (notice that the number of credits for course 3720 changed from 4 to 3):

DECLARE
revised CourseList :=
CourseList(Course(1002, 'Expository Writing', 3),
Course(2020, 'Film and Literature', 4),
Course(2810, 'Discursive Writing', 4),
Course(3010, 'Modern English Grammar ', 3),
Course(3550, 'Realism and Naturalism', 4),
Course(3720, 'Introduction to Shakespeare', 3),
Course(3760, 'Modern Drama', 4),
Course(3822, 'The Short Story', 4),
Course(3870, 'The American Novel', 5),
Course(4210, '20th-Century Poetry', 4),
Course(4725, 'Advanced Workshop in Poetry', 5));
num_changed INTEGER;
BEGIN
SELECT COUNT(*) INTO num_changed
FROM TABLE(CAST(revised AS CourseList)) new,
TABLE(SELECT courses FROM department
WHERE name = 'English') AS old
WHERE new.course_no = old.course_no AND
(new.title != old.title OR new.credits != old.credits);
dbms_output.put_line(num_changed);
END;

Using Collection Methods
The following collection methods help generalize code, make collections easier to use, and make your applications easier to maintain:

EXISTS
COUNT
LIMIT
FIRST and LAST
PRIOR and NEXT
EXTEND
TRIM
DELETE
A collection method is a built-in function or procedure that operates on collections and is called using dot notation. The syntax follows:

collection_name.method_name[(parameters)]


Collection methods cannot be called from SQL statements. Also, EXTEND and TRIM cannot be used with associative arrays. EXISTS, COUNT, LIMIT, FIRST, LAST, PRIOR, and NEXT are functions; EXTEND, TRIM, and DELETE are procedures. EXISTS, PRIOR, NEXT, TRIM, EXTEND, and DELETE take parameters corresponding to collection subscripts, which are usually integers but can also be strings for associative arrays.

Only EXISTS can be applied to atomically null collections. If you apply another method to such collections, PL/SQL raises COLLECTION_IS_NULL.

Checking If a Collection Element Exists (EXISTS Method)
EXISTS(n) returns TRUE if the nth element in a collection exists. Otherwise, EXISTS(n) returns FALSE. Mainly, you use EXISTS with DELETE to maintain sparse nested tables. You can also use EXISTS to avoid raising an exception when you reference a nonexistent element. In the following example, PL/SQL executes the assignment statement only if element i exists:

IF courses.EXISTS(i) THEN courses(i) := new_course; END IF;


When passed an out-of-range subscript, EXISTS returns FALSE instead of raising SUBSCRIPT_OUTSIDE_LIMIT.

Counting the Elements in a Collection (COUNT Method)
COUNT returns the number of elements that a collection currently contains. For instance, if varray projects contains 25 elements, the following IF condition is true:

IF projects.COUNT = 25 THEN ...


COUNT is useful because the current size of a collection is not always known. For example, if you fetch a column of Oracle data into a nested table, how many elements does the table contain? COUNT gives you the answer.

You can use COUNT wherever an integer expression is allowed. In the next example, you use COUNT to specify the upper bound of a loop range:

FOR i IN 1..courses.COUNT LOOP ...


For varrays, COUNT always equals LAST. For nested tables, COUNT normally equals LAST. But, if you delete elements from the middle of a nested table, COUNT becomes smaller than LAST.

When tallying elements, COUNT ignores deleted elements.

Checking the Maximum Size of a Collection (LIMIT Method)
For nested tables and associative arrays, which have no maximum size, LIMIT returns NULL. For varrays, LIMIT returns the maximum number of elements that a varray can contain (which you must specify in its type definition, and can change later with the TRIM and EXTEND methods). For instance, if the maximum size of varray PROJECTS is 25 elements, the following IF condition is true:

IF projects.LIMIT = 25 THEN ...


You can use LIMIT wherever an integer expression is allowed. In the following example, you use LIMIT to determine if you can add 15 more elements to varray projects:

IF (projects.COUNT + 15) < projects.LIMIT THEN ...

Finding the First or Last Collection Element (FIRST and LAST Methods)
FIRST and LAST return the first and last (smallest and largest) index numbers in a collection. For an associative array with VARCHAR2 key values, the lowest and highest key values are returned; ordering is based on the binary values of the characters in the string, unless the NLS_COMP initialization parameter is set to ANSI, in which case the ordering is based on the locale-specific sort order specified by the NLS_SORT initialization parameter.

If the collection is empty, FIRST and LAST return NULL.

If the collection contains only one element, FIRST and LAST return the same index value:

IF courses.FIRST = courses.LAST THEN ... -- only one element


The next example shows that you can use FIRST and LAST to specify the lower and upper bounds of a loop range provided each element in that range exists:

FOR i IN courses.FIRST..courses.LAST LOOP ...


In fact, you can use FIRST or LAST wherever an integer expression is allowed. In the following example, you use FIRST to initialize a loop counter:

i := courses.FIRST;
WHILE i IS NOT NULL LOOP ...


For varrays, FIRST always returns 1 and LAST always equals COUNT. For nested tables, FIRST normally returns 1. But, if you delete elements from the beginning of a nested table, FIRST returns a number larger than 1. Also for nested tables, LAST normally equals COUNT. But, if you delete elements from the middle of a nested table, LAST becomes larger than COUNT.

When scanning elements, FIRST and LAST ignore deleted elements.

Looping Through Collection Elements (PRIOR and NEXT Methods)
PRIOR(n) returns the index number that precedes index n in a collection. NEXT(n) returns the index number that succeeds index n. If n has no predecessor, PRIOR(n) returns NULL. Likewise, if n has no successor, NEXT(n) returns NULL.

For associative arrays with VARCHAR2 keys, these methods return the appropriate key value; ordering is based on the binary values of the characters in the string, unless the NLS_COMP initialization parameter is set to ANSI, in which case the ordering is based on the locale-specific sort order specified by the NLS_SORT initialization parameter.

These methods are more reliable than looping through a fixed set of subscript values, because elements might be inserted or deleted from the collection during the loop. This is especially true for associative arrays, where the subscripts might not be in consecutive order and so the sequence of subscripts might be (1,2,4,8,16) or ('A','E','I','O','U').

PRIOR and NEXT do not wrap from one end of a collection to the other. For example, the following statement assigns NULL to n because the first element in a collection has no predecessor:

n := courses.PRIOR(courses.FIRST); -- assigns NULL to n


PRIOR is the inverse of NEXT. For instance, if element i exists, the following statement assigns element i to itself:

projects (i):= projects. PRIOR(projects. NEXT (i));


You can use PRIOR or NEXT to traverse collections indexed by any series of subscripts. In the following example, you use NEXT to traverse a nested table from which some elements have been deleted:

i: = courses.FIRST; -- get subscript of first element
WHILE i IS NOT NULL LOOP
-- do something with courses (i)
i: = courses.NEXT (i); -- get subscript of next element
END LOOP;


When traversing elements, PRIOR and NEXT ignore deleted elements.

Increasing the Size of a Collection (EXTEND Method)
To increase the size of a nested table or varray, use EXTEND. You cannot use EXTEND with index-by tables.

This procedure has three forms:

EXTEND appends one null element to a collection.
EXTEND (n) appends n null elements to a collection.
EXTEND (n,i) appends n copies of the ith element to a collection.
For example, the following statement appends 5 copies of element 1 to nested table courses:

courses.EXTEND(5,1);


You cannot use EXTEND to initialize an atomically null collection. Also, if you impose the NOT NULL constraint on a TABLE or VARRAY type, you cannot apply the first two forms of EXTEND to collections of that type.

EXTEND operates on the internal size of a collection, which includes any deleted elements. So, if EXTEND encounters deleted elements, it includes them in its tally. PL/SQL keeps placeholders for deleted elements so that you can replace them if you wish. Consider the following example:

DECLARE
TYPE CourseList IS TABLE OF VARCHAR2(10);
courses CourseList;
BEGIN
courses := CourseList('Biol 4412', 'Psyc 3112', 'Anth 3001');
courses.DELETE(3); -- delete element 3
/* PL/SQL keeps a placeholder for element 3. So, the
next statement appends element 4, not element 3. */
courses.EXTEND; -- append one null element
/* Now element 4 exists, so the next statement does
not raise SUBSCRIPT_BEYOND_COUNT. */
courses(4) := 'Engl 2005';


When it includes deleted elements, the internal size of a nested table differs from the values returned by COUNT and LAST. For instance, if you initialize a nested table with five elements, then delete elements 2 and 5, the internal size is 5, COUNT returns 3, and LAST returns 4. All deleted elements (whether leading, in the middle, or trailing) are treated alike.

Decreasing the Size of a Collection (TRIM Method)
This procedure has two forms:

TRIM removes one element from the end of a collection.
TRIM(n) removes n elements from the end of a collection.
For example, this statement removes the last three elements from nested table courses:

courses.TRIM(3);


If n is too large, TRIM(n) raises SUBSCRIPT_BEYOND_COUNT.

TRIM operates on the internal size of a collection. So, if TRIM encounters deleted elements, it includes them in its tally. Consider the following example:

DECLARE
TYPE CourseList IS TABLE OF VARCHAR2(10);
courses CourseList;
BEGIN
courses := CourseList('Biol 4412', 'Psyc 3112', 'Anth 3001');
courses.DELETE(courses.LAST); -- delete element 3
/* At this point, COUNT equals 2, the number of valid
elements remaining. So, you might expect the next
statement to empty the nested table by trimming
elements 1 and 2. Instead, it trims valid element 2
and deleted element 3 because TRIM includes deleted
elements in its tally. */
courses.TRIM(courses.COUNT);
dbms_output.put_line(courses(1)); -- prints 'Biol 4412'


In general, do not depend on the interaction between TRIM and DELETE. It is better to treat nested tables like fixed-size arrays and use only DELETE, or to treat them like stacks and use only TRIM and EXTEND.

PL/SQL does not keep placeholders for trimmed elements. So, you cannot replace a trimmed element simply by assigning it a new value.

Deleting Collection Elements (DELETE Method)
This procedure has various forms:

DELETE removes all elements from a collection.
DELETE(n) removes the nth element from an associative array with a numeric key or a nested table. If the associative array has a string key, the element corresponding to the key value is deleted. If n is null, DELETE(n) does nothing.
DELETE(m,n) removes all elements in the range m..n from an associative array or nested table. If m is larger than n or if m or n is null, DELETE(m,n) does nothing.
For example:

BEGIN
courses.DELETE(2); -- deletes element 2
courses.DELETE(7,7); -- deletes element 7
courses.DELETE(6,3); -- does nothing
courses.DELETE(3,6); -- deletes elements 3 through 6

projects.DELETE; -- deletes all elements

nicknames.DELETE('Chip'); -- deletes element denoted by this key
nicknames.DELETE('Buffy','Fluffy'); -- deletes elements with keys
-- in this alphabetic range
END;


Varrays are dense, so you cannot delete their individual elements.

If an element to be deleted does not exist, DELETE simply skips it; no exception is raised. PL/SQL keeps placeholders for deleted elements. So, you can replace a deleted element simply by assigning it a new value.

DELETE lets you maintain sparse nested tables. In the following example, you retrieve nested table prospects into a temporary table, prune it, then store it back in the database:

DECLARE
my_prospects ProspectList;
revenue NUMBER;
BEGIN
SELECT prospects INTO my_prospects FROM customers WHERE ...
FOR i IN my_prospects.FIRST..my_prospects.LAST LOOP
estimate_revenue(my_prospects(i), revenue); -- call procedure
IF revenue < 25000 THEN
my_prospects.DELETE(i);
END IF;
END LOOP;
UPDATE customers SET prospects = my_prospects WHERE ...


The amount of memory allocated to a nested table can increase or decrease dynamically. As you delete elements, memory is freed page by page. If you delete the entire table, all the memory is freed.

Applying Methods to Collection Parameters
Within a subprogram, a collection parameter assumes the properties of the argument bound to it. So, you can apply the built-in collection methods (FIRST, LAST, COUNT, and so on) to such parameters. In the following example, a nested table is declared as the formal parameter of a packaged procedure:

CREATE PACKAGE personnel AS
TYPE Staff IS TABLE OF Employee;
...
PROCEDURE award_bonuses (members IN Staff);
END personnel;
CREATE PACKAGE BODY personnel AS
...
PROCEDURE award_bonuses (members IN Staff) IS
BEGIN
...
IF members.COUNT > 10 THEN -- apply method
...
END IF;
END;
END personnel;


Note: For varray parameters, the value of LIMIT is always derived from the parameter type definition, regardless of the parameter mode.

Avoiding Collection Exceptions
In most cases, if you reference a nonexistent collection element, PL/SQL raises a predefined exception. Consider the following example:

DECLARE
TYPE NumList IS TABLE OF NUMBER;
nums NumList; -- atomically null
BEGIN
/* Assume execution continues despite the raised exceptions. */
nums(1) := 1; -- raises COLLECTION_IS_NULL (1)
nums := NumList(1,2); -- initialize table
nums(NULL) := 3 -- raises VALUE_ERROR (2)
nums(0) := 3; -- raises SUBSCRIPT_OUTSIDE_LIMIT (3)
nums(3) := 3; -- raises SUBSCRIPT_BEYOND_COUNT (4)
nums.DELETE(1); -- delete element 1
IF nums(1) = 1 THEN ... -- raises NO_DATA_FOUND (5)


In the first case, the nested table is atomically null. In the second case, the subscript is null. In the third case, the subscript is outside the legal range. In the fourth case, the subscript exceeds the number of elements in the table. In the fifth case, the subscript designates a deleted element.

The following list shows when a given exception is raised:

Collection Exception Raised when...
COLLECTION_IS_NULL
you try to operate on an atomically null collection.

NO_DATA_FOUND
a subscript designates an element that was deleted, or a nonexistent element of an associative array.

SUBSCRIPT_BEYOND_COUNT
a subscript exceeds the number of elements in a collection.

SUBSCRIPT_OUTSIDE_LIMIT
a subscript is outside the allowed range.

VALUE_ERROR
a subscript is null or not convertible to the key type. This exception might occur if the key is defined as a PLS_INTEGER range, and the subscript is outside this range.


In some cases, you can pass invalid subscripts to a method without raising an exception. For instance, when you pass a null subscript to procedure DELETE, it does nothing. Also, you can replace deleted elements without raising NO_DATA_FOUND, as the following example shows:

DECLARE
TYPE NumList IS TABLE OF NUMBER;
nums NumList := NumList(10,20,30); -- initialize table
BEGIN
nums.DELETE(-1); -- does not raise SUBSCRIPT_OUTSIDE_LIMIT
nums.DELETE(3); -- delete 3rd element
dbms_output.put_line(nums.COUNT); -- prints 2
nums(3) := 30; -- allowed; does not raise NO_DATA_FOUND
dbms_output.put_line(nums.COUNT); -- prints 3
END;


Packaged collection types and local collection types are never compatible. For example, suppose you want to call the following packaged procedure:

CREATE PACKAGE pkg1 AS
TYPE NumList IS VARRAY(25) OF NUMBER(4);
PROCEDURE delete_emps (emp_list NumList);
END pkg1;

CREATE PACKAGE BODY pkg1 AS
PROCEDURE delete_emps (emp_list NumList) IS ...
...
END pkg1;


When you run the PL/SQL block below, the second procedure call fails with a wrong number or types of arguments error. That is because the packaged and local VARRAY types are incompatible even though their definitions are identical.

DECLARE
TYPE NumList IS VARRAY(25) OF NUMBER(4);
emps pkg1.NumList := pkg1.NumList(7369, 7499);
emps2 NumList := NumList(7521, 7566);
BEGIN
pkg1.delete_emps(emps);
pkg1.delete_emps(emps2); -- causes a compilation error
END;

Reducing Loop Overhead for Collections with Bulk Binds
As Figure 5-3 shows, the PL/SQL engine executes procedural statements but sends SQL statements to the SQL engine, which executes the SQL statements and, in some cases, returns data to the PL/SQL engine.

Figure 5-3 Context Switching

Text description of the illustration pls81027_context_switching.gif


Too many context switches between the PL/SQL and SQL engines can harm performance. That can happen when a loop executes a separate SQL statement for each element of a collection, specifying the collection element as a bind variable. For example, the following DELETE statement is sent to the SQL engine with each iteration of the FOR loop:

DECLARE
TYPE NumList IS VARRAY(20) OF NUMBER;
depts NumList := NumList(10, 30, 70); -- department numbers
BEGIN
...
FOR i IN depts.FIRST..depts.LAST LOOP
DELETE FROM emp WHERE deptno = depts(i);
END LOOP;
END;


In such cases, if the SQL statement affects four or more database rows, the use of bulk binds can improve performance considerably.

How Do Bulk Binds Improve Performance?
The assigning of values to PL/SQL variables in SQL statements is called binding. PL/SQL binding operations fall into three categories:

in-bind When a PL/SQL variable or host variable is stored in the database by an INSERT or UPDATE statement.
out-bind When a database value is assigned to a PL/SQL variable or a host variable by the RETURNING clause of an INSERT, UPDATE, or DELETE statement.
define When a database value is assigned to a PL/SQL variable or a host variable by a SELECT or FETCH statement.
A DML statement can transfer all the elements of a collection in a single operation, a process known as bulk binding. If the collection has 20 elements, bulk binding lets you perform the equivalent of 20 SELECT, INSERT, UPDATE, or DELETE statements using a single operation. This technique improves performance by minimizing the number of context switches between the PL/SQL and SQL engines. With bulk binds, entire collections, not just individual elements, are passed back and forth.

To do bulk binds with INSERT, UPDATE, and DELETE statements, you enclose the SQL statement within a PL/SQL FORALL statement.

To do bulk binds with SELECT statements, you include the BULK COLLECT clause in the SELECT statement instead of using INTO.

For full details of the syntax and restrictions for these statements, see "FORALL Statement" and "SELECT INTO Statement".

Example: Performing a Bulk Bind with DELETE
The following DELETE statement is sent to the SQL engine just once, even though it performs three DELETE operations:

DECLARE
TYPE NumList IS VARRAY(20) OF NUMBER;
depts NumList := NumList(10, 30, 70); -- department numbers
BEGIN
FORALL i IN depts.FIRST..depts.LAST
DELETE FROM emp WHERE deptno = depts(i);
END;


Example: Performing a Bulk Bind with INSERT
In the example below, 5000 part numbers and names are loaded into index-by tables. All table elements are inserted into a database table twice: first using a FOR loop, then using a FORALL statement. The FORALL version is much faster.

SQL> SET SERVEROUTPUT ON
SQL> CREATE TABLE parts (pnum NUMBER(4), pname CHAR(15));

Table created.

SQL> GET test.sql
1 DECLARE
2 TYPE NumTab IS TABLE OF NUMBER(4) INDEX BY BINARY_INTEGER;
3 TYPE NameTab IS TABLE OF CHAR(15) INDEX BY BINARY_INTEGER;
4 pnums NumTab;
5 pnames NameTab;
6 t1 NUMBER(5);
7 t2 NUMBER(5);
8 t3 NUMBER(5);
9
10
11 BEGIN
12 FOR j IN 1..5000 LOOP -- load index-by tables
13 pnums(j) := j;
14 pnames(j) := 'Part No. ' || TO_CHAR(j);
15 END LOOP;
16 t1 := dbms_utility.get_time;
17 FOR i IN 1..5000 LOOP -- use FOR loop
18 INSERT INTO parts VALUES (pnums(i), pnames(i));
19 END LOOP;
20 t2 := dbms_utility.get_time;
21 FORALL i IN 1..5000 -- use FORALL statement
22 INSERT INTO parts VALUES (pnums(i), pnames(i));
23 get_time(t3);
24 dbms_output.put_line('Execution Time (secs)');
25 dbms_output.put_line('---------------------');
26 dbms_output.put_line('FOR loop: ' || TO_CHAR(t2 - t1));
27 dbms_output.put_line('FORALL: ' || TO_CHAR(t3 - t2));
28* END;
SQL> /
Execution Time (secs)
---------------------
FOR loop: 32
FORALL: 3

PL/SQL procedure successfully completed.


Using the FORALL Statement
The keyword FORALL instructs the PL/SQL engine to bulk-bind input collections before sending them to the SQL engine. Although the FORALL statement contains an iteration scheme, it is not a FOR loop. Its syntax follows:

FORALL index IN lower_bound..upper_bound
sql_statement;


The index can be referenced only within the FORALL statement and only as a collection subscript. The SQL statement must be an INSERT, UPDATE, or DELETE statement that references collection elements. And, the bounds must specify a valid range of consecutive index numbers. The SQL engine executes the SQL statement once for each index number in the range.

Example: Using FORALL with Part of a Collection
As the following example shows, the bounds of the FORALL loop can apply to part of a collection, not necessarily all the elements:

DECLARE
TYPE NumList IS VARRAY(10) OF NUMBER;
depts NumList := NumList(20,30,50,55,57,60,70,75,90,92);
BEGIN
FORALL j IN 4..7 -- bulk-bind only part of varray
UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(j);
END;


Example: Bulk Bind Requires Subscripted Collection
The SQL statement can reference more than one collection. However, the PL/SQL engine bulk-binds only subscripted collections. So, in the following example, it does not bulk-bind the collection sals, which is passed to the function median:

FORALL i IN 1..20
INSERT INTO emp2 VALUES (enums(i), names(i), median(sals), ...);


Example: Inserting into an Object Table with FORALL
In addition to relational tables, the FORALL statement can manipulate object tables, as the following example shows:

CREATE TYPE PNum AS OBJECT (n NUMBER);
/
CREATE TABLE partno OF PNum;

DECLARE
TYPE NumTab IS TABLE OF NUMBER;
nums NumTab := NumTab(1, 2, 3, 4);
TYPE PNumTab IS TABLE OF PNum;
pnums PNumTab := PNumTab(PNum(1), PNum(2), PNum(3), PNum(4));
BEGIN
FORALL i IN pnums.FIRST..pnums.LAST
INSERT INTO partno VALUES(pnums(i));
FORALL i IN nums.FIRST..nums.LAST
DELETE FROM partno WHERE n = 2 * nums(i);
FORALL i IN nums.FIRST..nums.LAST
INSERT INTO partno VALUES(100 + nums(i));
END;

How FORALL Affects Rollbacks
In a FORALL statement, if any execution of the SQL statement raises an unhandled exception, all database changes made during previous executions are rolled back. However, if a raised exception is caught and handled, changes are rolled back to an implicit savepoint marked before each execution of the SQL statement. Changes made during previous executions are not rolled back. For example, suppose you create a database table that stores department numbers and job titles, as follows:

CREATE TABLE emp2 (deptno NUMBER(2), job VARCHAR2(15));


Next, you insert some rows into the table, as follows:

INSERT INTO emp2 VALUES(10, 'Clerk');
INSERT INTO emp2 VALUES(10, 'Clerk');
INSERT INTO emp2 VALUES(20, 'Bookkeeper'); -- 10-char job title
INSERT INTO emp2 VALUES(30, 'Analyst');
INSERT INTO emp2 VALUES(30, 'Analyst');


Then, you try to append the 7-character string ' (temp)' to certain job titles using the following UPDATE statement:

DECLARE
TYPE NumList IS TABLE OF NUMBER;
depts NumList := NumList(10, 20, 30);
BEGIN
FORALL j IN depts.FIRST..depts.LAST
UPDATE emp2 SET job = job || ' (temp)'
WHERE deptno = depts(j);
-- raises a "value too large" exception
EXCEPTION
WHEN OTHERS THEN
COMMIT;
END;


The SQL engine executes the UPDATE statement three times, once for each index number in the specified range, that is, once for depts(10), once for depts(20), and once for depts(30). The first execution succeeds, but the second execution fails because the string value 'Bookkeeper (temp)' is too large for the job column. In this case, only the second execution is rolled back.

When any execution of the SQL statement raises an exception, the FORALL statement halts. In our example, the second execution of the UPDATE statement raises an exception, so the third execution is never done.

Counting Rows Affected by FORALL Iterations with the %BULK_ROWCOUNT Attribute
To process SQL data manipulation statements, the SQL engine opens an implicit cursor named SQL. This cursor's scalar attributes, %FOUND, %ISOPEN, %NOTFOUND, and %ROWCOUNT, return useful information about the most recently executed SQL data manipulation statement.

The SQL cursor has one composite attribute, %BULK_ROWCOUNT, designed for use with the FORALL statement. This attribute has the semantics of an index-by table. Its ith element stores the number of rows processed by the ith execution of an INSERT, UPDATE or DELETE statement. If the ith execution affects no rows, %BULK_ROWCOUNT(i) returns zero. An example follows:

DECLARE
TYPE NumList IS TABLE OF NUMBER;
depts NumList := NumList(10, 20, 50);
BEGIN
FORALL j IN depts.FIRST..depts.LAST
UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(j);
-- Did the 3rd UPDATE statement affect any rows?
IF SQL%BULK_ROWCOUNT(3) = 0 THEN ...
END;


The FORALL statement and %BULK_ROWCOUNT attribute use the same subscripts. For example, if FORALL uses the range 5 .. 10, so does %BULK_ROWCOUNT.

%BULK_ROWCOUNT is usually equal to 1 for inserts, because a typical insert operation affects only a single row. But for the INSERT ... SELECT construct, %BULK_ROWCOUNT might be greater than 1. For example, the FORALL statement below inserts an arbitrary number of rows for each iteration. After each iteration, %BULK_ROWCOUNT returns the number of items inserted:

SET SERVEROUTPUT ON;
DECLARE
TYPE num_tab IS TABLE OF NUMBER;
deptnums num_tab;
BEGIN
SELECT deptno BULK COLLECT INTO deptnums FROM DEPT;

FORALL i IN 1..deptnums.COUNT
INSERT INTO emp_by_dept
SELECT empno, deptno FROM emp WHERE deptno =
deptnums(i);

FOR i IN 1..deptnums.COUNT LOOP
-- Count how many rows were inserted for each department; that is,
-- how many employees are in each department.
dbms_output.put_line('Dept '||deptnums(i)||': inserted '||
SQL%BULK_ROWCOUNT(i)||' records');
END LOOP;

dbms_output.put_line('Total records inserted =' || SQL%ROWCOUNT);
END;
/


You can also use the scalar attributes %FOUND, %NOTFOUND, and %ROWCOUNT with bulk binds. For example, %ROWCOUNT returns the total number of rows processed by all executions of the SQL statement.

%FOUND and %NOTFOUND refer only to the last execution of the SQL statement. However, you can use %BULK_ROWCOUNT to infer their values for individual executions. For example, when %BULK_ROWCOUNT(i) is zero, %FOUND and %NOTFOUND are FALSE and TRUE, respectively.

Handling FORALL Exceptions with the %BULK_EXCEPTIONS Attribute
PL/SQL provides a mechanism to handle exceptions raised during the execution of a FORALL statement. This mechanism enables a bulk-bind operation to save information about exceptions and continue processing.

To have a bulk bind complete despite errors, add the keywords SAVE EXCEPTIONS to your FORALL statement. The syntax follows:

FORALL index IN lower_bound..upper_bound SAVE EXCEPTIONS
{insert_stmt | update_stmt | delete_stmt}


All exceptions raised during the execution are saved in the new cursor attribute %BULK_EXCEPTIONS, which stores a collection of records. Each record has two fields. The first field, %BULK_EXCEPTIONS(i).ERROR_INDEX, holds the "iteration" of the FORALL statement during which the exception was raised. The second field, %BULK_EXCEPTIONS(i).ERROR_CODE, holds the corresponding Oracle error code.

The values stored by %BULK_EXCEPTIONS always refer to the most recently executed FORALL statement. The number of exceptions is saved in the count attribute of %BULK_EXCEPTIONS, that is, %BULK_EXCEPTIONS.COUNT. Its subscripts range from 1 to COUNT.

If you omit the keywords SAVE EXCEPTIONS, execution of the FORALL statement stops when an exception is raised. In that case, SQL%BULK_EXCEPTIONS.COUNT returns 1, and SQL%BULK_EXCEPTIONS contains just one record. If no exception is raised during execution, SQL%BULK_EXCEPTIONS.COUNT returns 0.

The following example shows how useful the cursor attribute %BULK_EXCEPTIONS can be:

DECLARE
TYPE NumList IS TABLE OF NUMBER;
num_tab NumList := NumList(10,0,11,12,30,0,20,199,2,0,9,1);
errors NUMBER;
dml_errors EXCEPTION;
PRAGMA exception_init(dml_errors, -24381);
BEGIN
FORALL i IN num_tab.FIRST..num_tab.LAST SAVE EXCEPTIONS
DELETE FROM emp WHERE sal > 500000/num_tab(i);
EXCEPTION
WHEN dml_errors THEN
errors := SQL%BULK_EXCEPTIONS.COUNT;
dbms_output.put_line('Number of errors is ' || errors);
FOR i IN 1..errors LOOP
dbms_output.put_line('Error ' || i || ' occurred during '||
'iteration ' || SQL%BULK_EXCEPTIONS(i).ERROR_INDEX);
dbms_output.put_line('Oracle error is ' ||
SQLERRM(-SQL%BULK_EXCEPTIONS(i).ERROR_CODE));
END LOOP;
END;


In this example, PL/SQL raised the predefined exception ZERO_DIVIDE when i equaled 2, 6, 10. After the bulk-bind completed, SQL%BULK_EXCEPTIONS.COUNT returned 3, and the contents of SQL%BULK_EXCEPTIONS were (2,1476), (6,1476), and (10,1476). To get the Oracle error message (which includes the code), we negated the value of SQL%BULK_EXCEPTIONS(i).ERROR_CODE and passed the result to the error-reporting function SQLERRM, which expects a negative number. Here is the output:

Number of errors is 3
Error 1 occurred during iteration 2
Oracle error is ORA-01476: divisor is equal to zero
Error 2 occurred during iteration 6
Oracle error is ORA-01476: divisor is equal to zero
Error 3 occurred during iteration 10
Oracle error is ORA-01476: divisor is equal to zero
Retrieving Query Results into Collections with the BULK COLLECT Clause
The keywords BULK COLLECT tell the SQL engine to bulk-bind output collections before returning them to the PL/SQL engine. You can use these keywords in the SELECT INTO, FETCH INTO, and RETURNING INTO clauses. Here is the syntax:

... BULK COLLECT INTO collection_name[, collection_name] ...


The SQL engine bulk-binds all collections referenced in the INTO list. The corresponding columns can store scalar or composite values including objects. In the following example, the SQL engine loads the entire empno and ename database columns into nested tables before returning the tables to the PL/SQL engine:

DECLARE
TYPE NumTab IS TABLE OF emp.empno%TYPE;
TYPE NameTab IS TABLE OF emp.ename%TYPE;
enums NumTab; -- no need to initialize
names NameTab;
BEGIN
SELECT empno, ename BULK COLLECT INTO enums, names FROM emp;
...
END;


In the next example, the SQL engine loads all the values in an object column into a nested table before returning the table to the PL/SQL engine:

CREATE TYPE Coords AS OBJECT (x NUMBER, y NUMBER);
CREATE TABLE grid (num NUMBER, loc Coords);
INSERT INTO grid VALUES(10, Coords(1,2));
INSERT INTO grid VALUES(20, Coords(3,4));

DECLARE
TYPE CoordsTab IS TABLE OF Coords;
pairs CoordsTab;
BEGIN
SELECT loc BULK COLLECT INTO pairs FROM grid;
-- now pairs contains (1,2) and (3,4)
END;


The SQL engine initializes and extends collections for you. (However, it cannot extend varrays beyond their maximum size.) Then, starting at index 1, it inserts elements consecutively and overwrites any pre-existent elements.

The SQL engine bulk-binds entire database columns. So, if a table has 50,000 rows, the engine loads 50,000 column values into the target collection. However, you can use the pseudocolumn ROWNUM to limit the number of rows processed. In the following example, you limit the number of rows to 100:

DECLARE
TYPE SalList IS TABLE OF emp.sal%TYPE;
sals SalList;
BEGIN
SELECT sal BULK COLLECT INTO sals FROM emp
WHERE ROWNUM <= 100;
...
END;

Examples of Bulk Fetching from a Cursor
Into One or More Collections
You can bulk-fetch from a cursor into one or more collections:

DECLARE
TYPE NameList IS TABLE OF emp.ename%TYPE;
TYPE SalList IS TABLE OF emp.sal%TYPE;
CURSOR c1 IS SELECT ename, sal FROM emp WHERE sal > 1000;
names NameList;
sals SalList;
BEGIN
OPEN c1;
FETCH c1 BULK COLLECT INTO names, sals;
END;


Into a Collection of Records
You can bulk-fetch from a cursor into a collection of records:

DECLARE
TYPE DeptRecTab IS TABLE OF dept%ROWTYPE;
dept_recs DeptRecTab;
CURSOR c1 IS
SELECT deptno, dname, loc FROM dept WHERE deptno > 10;
BEGIN
OPEN c1;
FETCH c1 BULK COLLECT INTO dept_recs;
END;


Limiting the Rows for a Bulk FETCH Operation with the LIMIT Clause
The optional LIMIT clause, allowed only in bulk (not scalar) FETCH statements, lets you limit the number of rows fetched from the database. The syntax is

FETCH ... BULK COLLECT INTO ... [LIMIT rows];


where rows can be a literal, variable, or expression but must evaluate to a number. Otherwise, PL/SQL raises the predefined exception VALUE_ERROR. If the number is not positive, PL/SQL raises INVALID_NUMBER. If necessary, PL/SQL rounds the number to the nearest integer.

In the example below, with each iteration of the loop, the FETCH statement fetches ten rows (or less) into index-by table empnos. The previous values are overwritten.

DECLARE
TYPE NumTab IS TABLE OF NUMBER INDEX BY BINARY_INTEGER;
CURSOR c1 IS SELECT empno FROM emp;
empnos NumTab;
rows NATURAL := 10;
BEGIN
OPEN c1;
LOOP
/* The following statement fetches 10 rows (or less). */
FETCH c1 BULK COLLECT INTO empnos LIMIT rows;
EXIT WHEN c1%NOTFOUND;
...
END LOOP;
CLOSE c1;
END;

Retrieving DML Results into a Collection with the RETURNING INTO Clause
You can use the BULK COLLECT clause in the RETURNING INTO clause of an INSERT, UPDATE, or DELETE statement, as the following example shows:

DECLARE
TYPE NumList IS TABLE OF emp.empno%TYPE;
enums NumList;
BEGIN
DELETE FROM emp WHERE deptno = 20
RETURNING empno BULK COLLECT INTO enums;
-- if there were five employees in department 20,
-- then enums contains five employee numbers
END;

Restrictions on BULK COLLECT
The following restrictions apply to the BULK COLLECT clause:

You cannot bulk collect into an associative array that has a string type for the key.
You can use the BULK COLLECT clause only in server-side programs (not in client-side programs). Otherwise, you get the error this feature is not supported in client-side programs.
All targets in a BULK COLLECT INTO clause must be collections, as the following example shows:
DECLARE
TYPE NameList IS TABLE OF emp.ename%TYPE;
names NameList;
salary emp.sal%TYPE;
BEGIN
SELECT ename, sal BULK COLLECT INTO names, salary -- illegal target
FROM emp WHERE ROWNUM < 50;
...
END;


Composite targets (such as objects) cannot be used in the RETURNING INTO clause. Otherwise, you get the error unsupported feature with RETURNING clause.
When implicit datatype conversions are needed, multiple composite targets cannot be used in the BULK COLLECT INTO clause.
When an implicit datatype conversion is needed, a collection of a composite target (such as a collection of objects) cannot be used in the BULK COLLECT INTO clause.
Using FORALL and BULK COLLECT Together
You can combine the BULK COLLECT clause with a FORALL statement, in which case, the SQL engine bulk-binds column values incrementally. In the following example, if collection depts has 3 elements, each of which causes 5 rows to be deleted, then collection enums has 15 elements when the statement completes:

FORALL j IN depts.FIRST..depts.LAST
DELETE FROM emp WHERE empno = depts(j)
RETURNING empno BULK COLLECT INTO enums;


The column values returned by each execution are added to the values returned previously. (With a FOR loop, the previous values are overwritten.)

You cannot use the SELECT ... BULK COLLECT statement in a FORALL statement. Otherwise, you get the error implementation restriction: cannot use FORALL and BULK COLLECT INTO together in SELECT statements.

Using Host Arrays with Bulk Binds
Client-side programs can use anonymous PL/SQL blocks to bulk-bind input and output host arrays. In fact, that is the most efficient way to pass collections to and from the database server.

Host arrays are declared in a host environment such as an OCI or Pro*C program and must be prefixed with a colon to distinguish them from PL/SQL collections. In the example below, an input host array is used in a DELETE statement. At run time, the anonymous PL/SQL block is sent to the database server for execution.

DECLARE
...
BEGIN
-- assume that values were assigned to the host array
-- and host variables in the host environment
FORALL i IN :lower..:upper
DELETE FROM emp WHERE deptno = :depts(i);
...
END;

What Is a Record?
A record is a group of related data items stored in fields, each with its own name and datatype. Suppose you have various data about an employee such as name, salary, and hire date. These items are logically related but dissimilar in type. A record containing a field for each item lets you treat the data as a logical unit. Thus, records make it easier to organize and represent information.

The attribute %ROWTYPE lets you declare a record that represents a row in a database table. However, you cannot specify the datatypes of fields in the record or declare fields of your own. The datatype RECORD lifts those restrictions and lets you define your own records.

Defining and Declaring Records
To create records, you define a RECORD type, then declare records of that type. You can define RECORD types in the declarative part of any PL/SQL block, subprogram, or package using the syntax

TYPE type_name IS RECORD (field_declaration[,field_declaration]...);


where field_declaration stands for

field_name field_type [[NOT NULL] {:= | DEFAULT} expression]


and where type_name is a type specifier used later to declare records, field_type is any PL/SQL datatype except REF CURSOR, and expression yields a value of the same type as field_type.

Note: Unlike VARRAY and (nested) TABLE types, RECORD types cannot be CREATEd and stored in the database.

You can use %TYPE and %ROWTYPE to specify field types. In the following example, you define a RECORD type named DeptRec:

DECLARE
TYPE DeptRec IS RECORD (
dept_id dept.deptno%TYPE,
dept_name VARCHAR2(14),
dept_loc VARCHAR2(13));
BEGIN
...
END;


Notice that field declarations are like variable declarations. Each field has a unique name and specific datatype. So, the value of a record is actually a collection of values, each of some simpler type.

As the example below shows, PL/SQL lets you define records that contain objects, collections, and other records (called nested records). However, object types cannot have attributes of type RECORD.

DECLARE
TYPE TimeRec IS RECORD (
seconds SMALLINT,
minutes SMALLINT,
hours SMALLINT);
TYPE FlightRec IS RECORD (
flight_no INTEGER,
plane_id VARCHAR2(10),
captain Employee, -- declare object
passengers PassengerList, -- declare varray
depart_time TimeRec, -- declare nested record
airport_code VARCHAR2(10));
BEGIN
...
END;


The next example shows that you can specify a RECORD type in the RETURN clause of a function specification. That allows the function to return a user-defined record of the same type.

DECLARE
TYPE EmpRec IS RECORD (
emp_id NUMBER(4)
last_name VARCHAR2(10),
dept_num NUMBER(2),
job_title VARCHAR2(9),
salary NUMBER(7,2));
...
FUNCTION nth_highest_salary (n INTEGER) RETURN EmpRec IS ...
BEGIN
...
END;


Declaring Records
Once you define a RECORD type, you can declare records of that type, as the example below shows. The identifier item_info represents an entire record.

DECLARE
TYPE StockItem IS RECORD (
item_no INTEGER(3),
description VARCHAR2(50),
quantity INTEGER,
price REAL(7,2));
item_info StockItem; -- declare record
BEGIN
...
END;


Like scalar variables, user-defined records can be declared as the formal parameters of procedures and functions. An example follows:

DECLARE
TYPE EmpRec IS RECORD (
emp_id emp.empno%TYPE,
last_name VARCHAR2(10),
job_title VARCHAR2(9),
salary NUMBER(7,2));
...
PROCEDURE raise_salary (emp_info EmpRec);
BEGIN
...
END;

Initializing Records
The example below shows that you can initialize a record in its type definition. When you declare a record of type TimeRec, its three fields assume an initial value of zero.

DECLARE
TYPE TimeRec IS RECORD (
secs SMALLINT := 0,
mins SMALLINT := 0,
hrs SMALLINT := 0);
BEGIN
...
END;


The next example shows that you can impose the NOT NULL constraint on any field, and so prevent the assigning of nulls to that field. Fields declared as NOT NULL must be initialized.

DECLARE
TYPE StockItem IS RECORD (
item_no INTEGER(3) NOT NULL := 999,
description VARCHAR2(50),
quantity INTEGER,
price REAL(7,2));
BEGIN
...
END;

Referencing Records
Unlike elements in a collection, which are accessed using subscripts, fields in a record are accessed by name. To reference an individual field, use dot notation and the following syntax:

record_name.field_name


For example, you reference field hire_date in record emp_info as follows:

emp_info.hire_date ...


When calling a function that returns a user-defined record, use the following syntax to reference fields in the record:

function_name(parameter_list).field_name


For example, the following call to function nth_highest_sal references the field salary in record emp_info:

DECLARE
TYPE EmpRec IS RECORD (
emp_id NUMBER(4),
job_title VARCHAR2(9),
salary NUMBER(7,2));
middle_sal NUMBER(7,2);
FUNCTION nth_highest_sal (n INTEGER) RETURN EmpRec IS
emp_info EmpRec;
BEGIN
...
RETURN emp_info; -- return record
END;
BEGIN
middle_sal := nth_highest_sal(10).salary; -- call function
...
END;


When calling a parameterless function, use the following syntax:

function_name().field_name -- note empty parameter list


To reference nested fields in a record returned by a function, use extended dot notation. The syntax follows:

function_name(parameter_list).field_name.nested_field_name


For instance, the following call to function item references the nested field minutes in record item_info:

DECLARE
TYPE TimeRec IS RECORD (minutes SMALLINT, hours SMALLINT);
TYPE AgendaItem IS RECORD (
priority INTEGER,
subject VARCHAR2(100),
duration TimeRec);
FUNCTION item (n INTEGER) RETURN AgendaItem IS
item_info AgendaItem;
BEGIN
...
RETURN item_info; -- return record
END;
BEGIN
...
IF item(3).duration.minutes > 30 THEN ... -- call function
END;


Also, use extended dot notation to reference the attributes of an object stored in a field, as the following example shows:

DECLARE
TYPE FlightRec IS RECORD (
flight_no INTEGER,
plane_id VARCHAR2(10),
captain Employee, -- declare object
passengers PassengerList, -- declare varray
depart_time TimeRec, -- declare nested record
airport_code VARCHAR2(10));
flight FlightRec;
BEGIN
...
IF flight.captain.name = 'H Rawlins' THEN ...
END;

Assigning Null Values to Records
To set all the fields in a record to null, simply assign to it an uninitialized record of the same type, as shown in the following example:

DECLARE
TYPE EmpRec IS RECORD (
emp_id emp.empno%TYPE,
job_title VARCHAR2(9),
salary NUMBER(7,2));
emp_info EmpRec;
emp_null EmpRec;
BEGIN
emp_info.emp_id := 7788;
emp_info.job_title := 'ANALYST';
emp_info.salary := 3500;
emp_info := emp_null; -- nulls all fields in emp_info
...
END;

Assigning Records
You can assign the value of an expression to a specific field in a record using the following syntax:

record_name.field_name := expression;


In the following example, you convert an employee name to upper case:

emp_info.ename := UPPER(emp_info.ename);


Instead of assigning values separately to each field in a record, you can assign values to all fields at once. This can be done in two ways. First, you can assign one user-defined record to another if they have the same datatype. Having fields that match exactly is not enough. Consider the following example:

DECLARE
TYPE DeptRec IS RECORD (
dept_num NUMBER(2),
dept_name VARCHAR2(14));
TYPE DeptItem IS RECORD (
dept_num NUMBER(2),
dept_name VARCHAR2(14));
dept1_info DeptRec;
dept2_info DeptItem;
BEGIN
...
dept1_info := dept2_info; -- illegal; different datatypes
END;


As the next example shows, you can assign a %ROWTYPE record to a user-defined record if their fields match in number and order, and corresponding fields have compatible datatypes:

DECLARE
TYPE DeptRec IS RECORD (
dept_num NUMBER(2),
dept_name VARCHAR2(14),
location VARCHAR2(13));
dept1_info DeptRec;
dept2_info dept%ROWTYPE;
BEGIN
SELECT * INTO dept2_info FROM dept WHERE deptno = 10;
dept1_info := dept2_info;
...
END;


Second, you can use the SELECT or FETCH statement to fetch column values into a record, as the example below shows. The columns in the select-list must appear in the same order as the fields in your record.

DECLARE
TYPE DeptRec IS RECORD (
dept_num NUMBER(2),
dept_name VARCHAR2(14),
location VARCHAR2(13));
dept_info DeptRec;
BEGIN
SELECT * INTO dept_info FROM dept WHERE deptno = 20;
...
END;


However, you cannot assign a list of values to a record using an assignment statement. The following syntax is not allowed:

record_name := (value1, value2, value3, ...); -- not allowed


The example below shows that you can assign one nested record to another if they have the same datatype. Such assignments are allowed even if the enclosing records have different datatypes.

DECLARE
TYPE TimeRec IS RECORD (mins SMALLINT, hrs SMALLINT);
TYPE MeetingRec IS RECORD (
day DATE,
time_of TimeRec, -- nested record
room_no INTEGER(4));
TYPE PartyRec IS RECORD (
day DATE,
time_of TimeRec, -- nested record
place VARCHAR2(25));
seminar MeetingRec;
party PartyRec;
BEGIN
...
party.time_of := seminar.time_of;
END;

Comparing Records
Records cannot be tested for nullity, equality, or inequality. For instance, the following IF conditions are not allowed:

BEGIN
...
IF emp_info IS NULL THEN ... -- illegal
IF dept2_info > dept1_info THEN ... -- illegal
END;

Manipulating Records
The datatype RECORD lets you collect information about the attributes of something. The information is easy to manipulate because you can refer to the collection as a whole. In the following example, you collect accounting figures from database tables assets and liabilities, then use ratio analysis to compare the performance of two subsidiary companies:

DECLARE
TYPE FiguresRec IS RECORD (cash REAL, notes REAL, ...);
sub1_figs FiguresRec;
sub2_figs FiguresRec;
FUNCTION acid_test (figs FiguresRec) RETURN REAL IS ...
BEGIN
SELECT cash, notes, ... INTO sub1_figs FROM assets, liabilities
WHERE assets.sub = 1 AND liabilities.sub = 1;
SELECT cash, notes, ... INTO sub2_figs FROM assets, liabilities
WHERE assets.sub = 2 AND liabilities.sub = 2;
IF acid_test(sub1_figs) > acid_test(sub2_figs) THEN ...
...
END;


Notice how easy it is to pass the collected figures to the function acid_test, which computes a financial ratio.

In SQL*Plus, suppose you define object type Passenger, as follows:

SQL> CREATE TYPE Passenger AS OBJECT(
2 flight_no NUMBER(3),
3 name VARCHAR2(20),
4 seat CHAR(5));


Next, you define VARRAY type PassengerList, which stores Passenger objects:

SQL> CREATE TYPE PassengerList AS VARRAY(300) OF Passenger;


Finally, you create relational table flights, which has a column of type PassengerList, as follows:

SQL> CREATE TABLE flights (
2 flight_no NUMBER(3),
3 gate CHAR(5),
4 departure CHAR(15),
5 arrival CHAR(15),
6 passengers PassengerList);


Each item in column passengers is a varray that will store the passenger list for a given flight. Now, you can populate database table flights, as follows:

BEGIN
INSERT INTO flights
VALUES(109, '80', 'DFW 6:35PM', 'HOU 7:40PM',
PassengerList(Passenger(109, 'Paula Trusdale', '13C'),
Passenger(109, 'Louis Jemenez', '22F'),
Passenger(109, 'Joseph Braun', '11B'), ...));
INSERT INTO flights
VALUES(114, '12B', 'SFO 9:45AM', 'LAX 12:10PM',
PassengerList(Passenger(114, 'Earl Benton', '23A'),
Passenger(114, 'Alma Breckenridge', '10E'),
Passenger(114, 'Mary Rizutto', '11C'), ...));
INSERT INTO flights
VALUES(27, '34', 'JFK 7:05AM', 'MIA 9:55AM',
PassengerList(Passenger(27, 'Raymond Kiley', '34D'),
Passenger(27, 'Beth Steinberg', '3A'),
Passenger(27, 'Jean Lafevre', '19C'), ...));
END;


In the example below, you fetch rows from database table flights into record flight_info. That way, you can treat all the information about a flight, including its passenger list, as a logical unit.

DECLARE
TYPE FlightRec IS RECORD (
flight_no NUMBER(3),
gate CHAR(5),
departure CHAR(15),
arrival CHAR(15),
passengers PassengerList);
flight_info FlightRec;
CURSOR c1 IS SELECT * FROM flights;
seat_not_available EXCEPTION;
BEGIN
OPEN c1;
LOOP
FETCH c1 INTO flight_info;
EXIT WHEN c1%NOTFOUND;
FOR i IN 1..flight_info.passengers.LAST LOOP
IF flight_info.passengers(i).seat = 'NA' THEN
dbms_output.put_line(flight_info.passengers(i).name);
RAISE seat_not_available;
END IF;
...
END LOOP;
END LOOP;
CLOSE c1;
EXCEPTION
WHEN seat_not_available THEN
...
END;

Inserting PL/SQL Records into the Database
A PL/SQL-only extension of the INSERT statement lets you insert records into database rows using a single variable of type RECORD or %ROWTYPE instead of a list of fields. That makes your code more readable and maintainable.

The number of fields in the record must equal the number of columns listed in the INTO clause, and corresponding fields and columns must have compatible datatypes. To make sure the record is compatible with the table, you might find it most convenient to declare the variable as the type table_name%ROWTYPE.

Inserting a PL/SQL Record Using %ROWTYPE: Example
This example declares a record variable using a %ROWTYPE qualifier. You can insert this variable without specifying a column list. The %ROWTYPE declaration ensures that the record attributes have exactly the same names and types as the table columns.

DECLARE
dept_info dept%ROWTYPE;
BEGIN
-- deptno, dname, and loc are the table columns.
-- The record picks up these names from the %ROWTYPE.
dept_info.deptno := 70;
dept_info.dname := 'PERSONNEL';
dept_info.loc := 'DALLAS';
-- Using the %ROWTYPE means we can leave out the column list
-- (deptno, dname, loc) from the INSERT statement.
INSERT INTO dept VALUES dept_info;
END;

Updating the Database with PL/SQL Record Values
A PL/SQL-only extension of the UPDATE statement lets you update database rows using a single variable of type RECORD or %ROWTYPE instead of a list of fields.

The number of fields in the record must equal the number of columns listed in the SET clause, and corresponding fields and columns must have compatible datatypes.

Updating a Row Using a Record: Example
You can use the keyword ROW to represent an entire row:

DECLARE
dept_info dept%ROWTYPE;
BEGIN
dept_info.deptno := 30;
dept_info.dname := 'MARKETING';
dept_info.loc := 'ATLANTA';
-- The row will have values for the filled-in columns, and null
-- for any other columns.
UPDATE dept SET ROW = dept_info WHERE deptno = 30;
END;


The keyword ROW is allowed only on the left side of a SET clause.

SET ROW Not Allowed with Subquery: Example
You cannot use ROW with a subquery. For example, the following UPDATE statement is not allowed:

UPDATE emp SET ROW = (SELECT * FROM mgrs); -- not allowed


Updating a Row Using a Record Containing an Object: Example
Records containing object types are allowed:

CREATE TYPE Worker AS OBJECT (name VARCHAR2(25), dept VARCHAR2(15));
/
CREATE TABLE teams (team_no NUMBER, team_member Worker);

DECLARE
team_rec teams%ROWTYPE;
BEGIN
team_rec.team_no := 5;
team_rec.team_member := Worker('Paul Ocker', 'Accounting');
UPDATE teams SET ROW = team_rec;
END;
/


Updating a Row Using a Record Containing a Collection: Example
The record can also contain collections:

CREATE TYPE Worker AS OBJECT (name VARCHAR2(25), dept VARCHAR2(15));
/
CREATE TYPE Roster AS TABLE OF Worker;
/
CREATE TABLE teams (team_no NUMBER, members Roster)
NESTED TABLE members STORE AS teams_store;

INSERT INTO teams VALUES (1, Roster(
Worker('Paul Ocker', 'Accounting'),
Worker('Gail Chan', 'Sales')
Worker('Marie Bello', 'Operations')
Worker('Alan Conwright', 'Research')));

DECLARE
team_rec teams%ROWTYPE;
BEGIN
team_rec.team_no := 3;
team_rec.members := Roster(
Worker('William Bliss', 'Sales'),
Worker('Ana Lopez', 'Sales')
Worker('Bridget Towner', 'Operations')
Worker('Ajay Singh', 'Accounting'));
UPDATE teams SET ROW = team_rec;
END;
/


Using the RETURNING Clause with a Record: Example
The INSERT, UPDATE, and DELETE statements can include a RETURNING clause, which returns column values from the affected row into a PL/SQL record variable. This eliminates the need to SELECT the row after an insert or update, or before a delete. You can use this clause only when operating on exactly one row.

In the following example, you update the salary of an employee and, at the same time, retrieve the employee's name, job title, and new salary into a record variable:

DECLARE
TYPE EmpRec IS RECORD (
emp_name VARCHAR2(10),
job_title VARCHAR2(9),
salary NUMBER(7,2));
emp_info EmpRec;
emp_id NUMBER(4);
BEGIN
emp_id := 7782;
UPDATE emp SET sal = sal * 1.1
WHERE empno = emp_id
RETURNING ename, job, sal INTO emp_info;
END;

Restrictions on Record Inserts/Updates
Currently, the following restrictions apply to record inserts/updates:

Record variables are allowed only in the following places:
On the right side of the SET clause in an UPDATE statement
In the VALUES clause of an INSERT statement
In the INTO subclause of a RETURNING clause
Record variables are not allowed in a SELECT list, WHERE clause, GROUP BY clause, or ORDER BY clause.

The keyword ROW is allowed only on the left side of a SET clause. Also, you cannot use ROW with a subquery.
In an UPDATE statement, only one SET clause is allowed if ROW is used.
If the VALUES clause of an INSERT statement contains a record variable, no other variable or value is allowed in the clause.
If the INTO subclause of a RETURNING clause contains a record variable, no other variable or value is allowed in the subclause.
The following are not supported:
Nested record types
Functions that return a record
Record inserts/updates using the EXECUTE IMMEDIATE statement.
Querying Data into Collections of Records
PL/SQL binding operations fall into three categories:

define Refers to database values retrieved by a SELECT or FETCH statement into PL/SQL variables or host variables.
in-bind Refers to database values inserted by an INSERT statement or modified by an UPDATE statement.
out-bind Refers to database values returned by the RETURNING clause of an INSERT, UPDATE, or DELETE statement into PL/SQL variables or host variables.
PL/SQL supports the bulk binding of collections of records in DML statements. Specifically, a define or out-bind variable can be a collection of records, and in-bind values can be stored in a collection of records. The syntax follows:

SELECT select_items BULK COLLECT INTO record_variable_name
FROM rest_of_select_stmt

FETCH { cursor_name
| cursor_variable_name
| :host_cursor_variable_name}
BULK COLLECT INTO record_variable_name
[LIMIT numeric_expression];

FORALL index IN lower_bound..upper_bound
INSERT INTO { table_reference
| THE_subquery} [{column_name[, column_name]...}]
VALUES (record_variable_name(index)) rest_of_insert_stmt

FORALL index IN lower_bound..upper_bound
UPDATE {table_reference | THE_subquery} [alias]
SET (column_name[, column_name]...) = record_variable_name(index)
rest_of_update_stmt

RETURNING row_expression[, row_expression]...
BULK COLLECT INTO record_variable_name;


In each statement and clause above, the record variable stores a collection of records. The number of fields in the record must equal the number of items in the SELECT list, the number of columns in the INSERT INTO clause, the number of columns in the UPDATE ... SET clause, or the number of row expressions in the RETURNING clause, respectively. Corresponding fields and columns must have compatible datatypes. Here are several examples:

CREATE TABLE tab1 (col1 NUMBER, col2 VARCHAR2(20));
/
CREATE TABLE tab2 (col1 NUMBER, col2 VARCHAR2(20));
/
DECLARE
TYPE RecTabTyp IS TABLE OF tab1%ROWTYPE
INDEX BY BINARY_INTEGER;
TYPE NumTabTyp IS TABLE OF NUMBER
INDEX BY BINARY_INTEGER;
TYPE CharTabTyp IS TABLE OF VARCHAR2(20)
INDEX BY BINARY_INTEGER;
CURSOR c1 IS SELECT col1, col2 FROM tab2;
rec_tab RecTabTyp;
num_tab NumTabTyp := NumTabTyp(2,5,8,9);
char_tab CharTabTyp := CharTabTyp('Tim', 'Jon', 'Beth', 'Jenny');
BEGIN
FORALL i IN 1..4
INSERT INTO tab1 VALUES(num_tab(i), char_tab(i));

SELECT col1, col2 BULK COLLECT INTO rec_tab FROM tab1
WHERE col1 < 9;

FORALL i IN rec_tab.FIRST..rec_tab.LAST
INSERT INTO tab2 VALUES rec_tab(i);

FOR i IN rec_tab.FIRST..rec_tab.LAST LOOP
rec_tab(i).col1 := rec_tab(i).col1 + 100;
END LOOP;

FORALL i IN rec_tab.FIRST..rec_tab.LAST
UPDATE tab1 SET (col1, col2) = rec_tab(i) WHERE col1 < 8;

OPEN c1;
FETCH c1 BULK COLLECT INTO rec_tab;
CLOSE c1;
END;



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