DECLARE condition_name CONDITION FOR condition_value

condition_value:
    mysql_error_code
  | SQLSTATE [VALUE] sqlstate_value

The DECLARE ... CONDITION statement declares a named error condition, associating a name with a condition that needs specific handling. The name can be referred to in a subsequent DECLARE ... HANDLER statement (see Section 13.6.7.2, “DECLARE ... HANDLER Syntax”).

Condition declarations must appear before cursor or handler declarations.

The condition_value for DECLARE ... CONDITION can be a MySQL error code (a number) or an SQLSTATE value (a 5-character string literal). You should not use MySQL error code 0 or SQLSTATE values that begin with '00', because those indicate success rather than an error condition. For a list of MySQL error codes and SQLSTATE values, see Section C.3, “Server Error Codes and Messages”.

Using names for conditions can help make stored program code clearer. For example, this handler applies to attempts to drop a nonexistent table, but that is apparent only if you know the meaning of MySQL error code 1051:

DECLARE CONTINUE HANDLER FOR 1051
  BEGIN
    -- body of handler
  END;

By declaring a name for the condition, the purpose of the handler is more readily seen:

DECLARE no_such_table CONDITION FOR 1051;
DECLARE CONTINUE HANDLER FOR no_such_table
  BEGIN
    -- body of handler
  END;

Here is a named condition for the same condition, but based on the corresponding SQLSTATE value rather than the MySQL error code:

DECLARE no_such_table CONDITION FOR SQLSTATE '42S02';
DECLARE CONTINUE HANDLER FOR no_such_table
  BEGIN
    -- body of handler
END;