MySQL 9.4 Release Notes
        
[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]
        The statement list within a WHILE
        statement is repeated as long as the
        search_condition expression is true.
        statement_list consists of one or
        more SQL statements, each terminated by a semicolon
        (;) statement delimiter.
      
        A WHILE statement can be labeled.
        For the rules regarding label use, see
        Section 15.6.2, “Statement Labels”.
      
Example:
CREATE PROCEDURE dowhile()
BEGIN
  DECLARE v1 INT DEFAULT 5;
  WHILE v1 > 0 DO
    ...
    SET v1 = v1 - 1;
  END WHILE;
END;