13.6.2 Statement Label Syntax

Labels are permitted for BEGIN ... END blocks and for the LOOP, REPEAT, and the WHILE statements.Label use for those statements follows these rules:

• begin_label must be followed by a colon.
• begin_label can be given without end_label. if end_label is present, it must be the same as begin_label.
• end_label cannot be given without begin_label.
• Labels at the same nesting level must be distinct.
• Labels can be up to 16 characters long

To refer to a label within the labeled construct, use and ITERATE or LEAVE statement. The following example uses those statements to continue iterating or terminate the loop:

mysql> CREATE PROCEDURE doiterate(p1 INT)
    -> BEGIN
    ->   label1: LOOP
    ->     SET p1 = p1 + 1;
    ->     IF p1 < 10 THEN ITERATE label1; END IF;
    ->     LEAVE label1;
    ->   END LOOP label1;
    -> END$$

The scope of a block label does not include the code for handlers declared within the block. For details, see Section 13.6.7.2 "DECLARE ... HANDLER Syntax".