Sybase 12.4.2 manual Using exception handlers in procedures, 261

CHAPTER 6 Using Procedures and Batches

The procedures both continued executing after the warning was generated, with SQLSTATE set by the warning (02000).

Using exception handlers in procedures

It is often desirable to intercept certain types of errors and handle them within a procedure, rather than pass the error back to the calling environment. This is done through the use of an exception handler.

An exception handler is defined with the EXCEPTION part of a compound statement (see “Using compound statements” on page 240). The exception handler is executed whenever an error occurs in the compound statement. Unlike errors, warnings do not cause exception handling code to be executed. Exception handling code is also executed if an error is encountered in a nested compound statement or in a procedure that has been invoked anywhere within the compound statement.

Drop the procedures Remember to drop both the InnerProc and OuterProc procedures before continuing with the tutorial. You can do this by entering the following commands in the command window:

DROP PROCEDURE OUTERPROC;

DROP PROCEDURE INNERPROC

The demonstration procedures used to illustrate exception handling are based on those used in “Default error handling in procedures” on page 256 In this case, additional code is added to handle the column not found error in the InnerProc procedure.

CREATE PROCEDURE OuterProc()

BEGIN

MESSAGE ’Hello from OuterProc.’;

CALL InnerProc();

MESSAGE ’SQLSTATE set to ’,

SQLSTATE,’ in OuterProc.’

END

CREATE PROCEDURE InnerProc()

BEGIN

DECLARE column_not_found

EXCEPTION FOR SQLSTATE ’52003’;

MESSAGE ’Hello from InnerProc.’;

SIGNAL column_not_found;

MESSAGE ’Line following SIGNAL.’;

EXCEPTION

WHEN column_not_found THEN

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