Exceptions 1: Named System Exceptions

What is a named system exception?
Named system exceptions are exceptions that have been given names by PL/SQL. They are named in the STANDARD package in PL/SQL and do not need to be defined by the programmer.

Oracle has a standard set of exceptions already named as follows:



Oracle/PLSQL: Named System Exceptions

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The syntax for the Named System Exception in a procedure is:

CREATE [OR REPLACE] PROCEDURE procedure_name
[ (parameter [,parameter]) ]
IS
[declaration_section]
BEGIN
executable_section

EXCEPTION
WHEN exception_name1 THEN
[statements]

WHEN exception_name2 THEN
[statements]

WHEN exception_name_n THEN
[statements]

WHEN OTHERS THEN
[statements]

END [procedure_name];




The syntax for the Named System Exception in a function is:

CREATE [OR REPLACE] FUNCTION function_name
[ (parameter [,parameter]) ]
RETURN return_datatype
IS | AS
[declaration_section]
BEGIN
executable_section

EXCEPTION
WHEN exception_name1 THEN
[statements]

WHEN exception_name2 THEN
[statements]

WHEN exception_name_n THEN
[statements]

WHEN OTHERS THEN
[statements]

END [function_name];



Here is an example of a procedure that uses a Named System Exception:

CREATE OR REPLACE PROCEDURE add_new_supplier
(supplier_id_in IN NUMBER, supplier_name_in IN VARCHAR2)
IS

BEGIN
INSERT INTO suppliers (supplier_id, supplier_name )
VALUES ( supplier_id_in, supplier_name_in );

EXCEPTION
WHEN DUP_VAL_ON_INDEX THEN
raise_application_error (-20001,'You have tried to insert a duplicate supplier_id.');

WHEN OTHERS THEN
raise_application_error (-20002,'An error has occurred inserting a supplier.');

END;

In this example, we are trapping the Named System Exception called DUP_VAL_ON_INDEX. We are also using the WHEN OTHERS clause to trap all remaining exceptions.