ORACLE/PLSQL: NAMED SYSTEM EXCEPTIONS

WHAT IS A NAMED SYSTEM EXCEPTION IN ORACLE?

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 Exception Name	Oracle Error	Explanation
DUP_VAL_ON_INDEX	ORA-00001	You tried to execute an INSERT or UPDATE statement that has created a duplicate value in a field restricted by a unique index.
TIMEOUT_ON_RESOURCE	ORA-00051	You were waiting for a resource and you timed out.
TRANSACTION_BACKED_OUT	ORA-00061	The remote portion of a transaction has rolled back.
INVALID_CURSOR	ORA-01001	You tried to reference a cursor that does not yet exist. This may have happened because you've executed a FETCH cursor or CLOSE cursor before OPENing the cursor.
NOT_LOGGED_ON	ORA-01012	You tried to execute a call to Oracle before logging in.
LOGIN_DENIED	ORA-01017	You tried to log into Oracle with an invalid username/password combination.
NO_DATA_FOUND	ORA-01403	You tried one of the following: You executed a SELECT INTO statement and no rows were returned. You referenced an uninitialized row in a table. You read past the end of file with the UTL_FILE package.
TOO_MANY_ROWS	ORA-01422	You tried to execute a SELECT INTO statement and more than one row was returned.
ZERO_DIVIDE	ORA-01476	You tried to divide a number by zero.
INVALID_NUMBER	ORA-01722	You tried to execute a SQL statement that tried to convert a string to a number, but it was unsuccessful.
STORAGE_ERROR	ORA-06500	You ran out of memory or memory was corrupted.
PROGRAM_ERROR	ORA-06501	This is a generic "Contact Oracle support" message because an internal problem was encountered.
VALUE_ERROR	ORA-06502	You tried to perform an operation and there was a error on a conversion, truncation, or invalid constraining of numeric or character data.
CURSOR_ALREADY_OPEN	ORA-06511	You tried to open a cursor that is already open.

SYNTAX

We will take a look at the syntax for Named System Exceptions in both procedures and functions.

Syntax for Procedures

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];

Syntax for Functions

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];

EXAMPLE

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.

I hope you all have enjoyed reading this article. Comments are welcome....