PL/SQL Tutorials - HANDLING ERRORS AND EXCEPTIONS
PLSQL handles the errors caused at the server level and publishes them using the following functions:
EXCEPTION This datatype is declared in DECLARE section of the PLSQL code enables to call those as and when they are required.
An internal exception is raised implicitly whenever your PL/SQL program violates an Oracle rule or exceeds a system-dependent limit. Every Oracle error has a number, but exceptions must be handled by name. So, PL/SQL predefines some common Oracle errors as exceptions. For example, PL/SQL raises the predefined exception NO_DATA_FOUND if a SELECT INTO statement returns no rows.
To handle other Oracle errors, you can use the OTHERS handler.
The functions SQLCODE and SQLERRM are especially useful in the OTHERS handler because they return the Oracle error code and message text. Alternatively, you can use the pragma EXCEPTION_INIT to associate exception names with Oracle error codes.
Oracle Error: ORA-06530
Your program attempts to assign values to the attributes of an uninitialized (atomically null) object.
Oracle Error: ORA-06592
None of the choices in the WHEN clauses of a CASE statement is selected, and there is no ELSE clause.
Oracle Error: ORA-06531
Your program attempts to apply collection methods other than EXISTS to an uninitialized (atomically null) nested table or varray, or the program attempts to assign values to the elements of an uninitialized nested table or varray.
Oracle Error: ORA-06511
Your program attempts to open an already open cursor. A cursor must be closed before it can be reopened. A cursor FOR loop automatically opens the cursor to which it refers. So, your program cannot open that cursor inside the loop.
Oracle Error: ORA-00001
Your program attempts to store duplicate values in a database column that is constrained by a unique index.
Oracle Error: ORA-01001
Your program attempts an illegal cursor operation such as closing an unopened cursor.
Oracle Error: ORA-01722
In a SQL statement, the conversion of a character string into a number fails because the string does not represent a valid number. (In procedural statements, VALUE_ERROR is raised.) This exception is also raised when the LIMIT-clause expression in a bulk FETCH statement does not evaluate to a positive number.
Oracle Error: ORA-01017
Your program attempts to log on to Oracle with an invalid username and/or password.
Oracle Error: ORA-01403
A SELECT INTO statement returns no rows, or your program references a deleted element in a nested table or an un-initialized element in an index-by table. SQL aggregate functions such as AVG and SUM always return a value or a null. So, a SELECT INTO statement that calls an aggregate function never raises NO_DATA_FOUND. The FETCH statement is expected to return no rows eventually, so when that happens, no exception is raised.
Oracle Error: ORA-01012
Your program issues a database call without being connected to Oracle.
Oracle Error: ORA-06501
PL/SQL has an internal problem.
Oracle Error: ORA-06504
The host cursor variable and PL/SQL cursor variable involved in an assignment have incompatible return types. For example, when an open host cursor variable is passed to a stored subprogram, the return types of the actual and formal parameters must be compatible.
Oracle Error: ORA-30625
Your program attempts to call a MEMBER method on a null instance. That is, the built-in parameter SELF (which is always the first parameter passed to a MEMBER method) is null.
Oracle Error: ORA-06500
PL/SQL runs out of memory or memory has been corrupted.
Oracle Error: ORA-06533
Your program references a nested table or varray element using an index number larger than the number of elements in the collection.
Oracle Error: ORA-06532
Your program references a nested table or varray element using an index number (-1 for example) that is outside the legal range.
Oracle Error: ORA-01410
The conversion of a character string into a universal rowid fails because the character string does not represent a valid rowid.
Oracle Error: ORA-00051
A time-out occurs while Oracle is waiting for a resource.
Oracle Error: ORA-01422
A SELECT INTO statement returns more than one row.
Oracle Error: ORA-06502
An arithmetic, conversion, truncation, or size-constraint error occurs. For example, when your program selects a column value into a character variable, if the value is longer than the declared length of the variable, PL/SQL aborts the assignment and raises VALUE_ERROR. In procedural statements, VALUE_ERROR is raised if the conversion of a character string into a number fails. (In SQL statements, INVALID_NUMBER is raised.)
Oracle Error: ORA-01476
Your program attempts to divide a number by zero.
An Example of handling exception (from Oracle Docs)
DECLARE ---------- sub-block begins
past_due EXCEPTION; -- this declaration prevails
IF ... THEN
RAISE past_due; -- this is not handled
END; ------------- sub-block ends
WHEN past_due THEN -- does not handle RAISE exception