Why PL/SQL Exceptions Exceptions?

Using exceptions for error handling has several advantages. Without exception handling, every time you issue a command, you must check for execution errors:

BEGIN

   SELECT ...

      -- check for 'no data found' error

   SELECT ...

      -- check for 'no data found' error

   SELECT ...

      -- check for 'no data found' error

Error processing is not clearly separated from normal processing; nor is it robust. If you neglect to code a check, the error goes undetected and is likely to cause other, seemingly unrelated errors.

With exceptions, you can handle errors conveniently without the need to code multiple checks, as follows:

BEGIN

   SELECT ...

   SELECT ...

   SELECT ...

   ...

EXCEPTION

   WHEN NO_DATA_FOUND THEN  -- catches all 'no data found' errors

Exceptions improve readability by letting you isolate error-handling routines. Exceptions also improve reliability. You need not worry about checking for an error at every point it might occur. Just add an exception handler to your PL/SQL block. If the exception is ever raised in that block (or any sub-block), you can be sure it will be handled.