[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. 只要搜索条件表达式为true，WHILE语句中的语句列表就会重复。statement_list consists of one or more SQL statements, each terminated by a semicolon (;) statement delimiter.statement_list由一个或多个SQL语句组成，每个语句以分号（；）结尾语句分隔符。

A WHILE statement can be labeled. For the rules regarding label use, see Section 13.6.2, “Statement Labels”.可以标记WHILE语句。有关标签使用的规则，请参阅第13.6.2节，“声明标签”。

Example:例子：

CREATE PROCEDURE dowhile()
BEGIN
  DECLARE v1 INT DEFAULT 5;

  WHILE v1 > 0 DO
    ...
    SET v1 = v1 - 1;
  END WHILE;
END;