MySQL Reference Manual for version 4.0.18.

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18.1.7.2 DECLARE Handlers

 
DECLARE handler_type HANDLER FOR condition_value[,...] sp_statement

handler_type:
    CONTINUE
  | EXIT
  | UNDO

condition_value:
    SQLSTATE [VALUE] sqlstate_value
  | condition_name
  | SQLWARNING
  | NOT FOUND
  | SQLEXCEPTION
  | mysql_error_code

This statement specifies handlers that each may deal with one or more conditions. If one of these conditions occurs, the specified statement is executed.

For a CONTINUE handler, execution of the current routine continues after execution of the handler statement. For an EXIT handler, execution of the current routine is terminated. The UNDO handler_type is not yet supported. UNDO currently behaves like CONTINUE.

In addition to SQLSTATE values, MySQL error codes are also supported.

For example:

 
mysql> CREATE TABLE test.t (s1 int,primary key (s1));
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter |

mysql> CREATE PROCEDURE handlerdemo ()
    -> BEGIN
    ->   DECLARE CONTINUE HANDLER FOR '23000' SET @x2 = 1;
    ->   set @x = 1;
    ->   INSERT INTO test.t VALUES (1);
    ->   set @x = 2;
    ->   INSERT INTO test.t VALUES (1);
    ->   SET @x = 3;
    -> END;
    -> |
Query OK, 0 rows affected (0.00 sec)

mysql> CALL handlerdemo()|
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT @x|
    +------+
    | @x   |
    +------+
    | 3    |
    +------+
    1 row in set (0.00 sec)

Notice that @x is 3, which shows that MySQL executed to the end of the procedure. If the line DECLARE CONTINUE HANDLER FOR '23000' SET @x2 = 1; had not been present, MySQL would have taken the default (EXIT) path after the second INSERT failed due to the PRIMARY KEY constraint, and SELECT @x would have returned 2.


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