MySQL supports the IF, CASE, ITERATE, LEAVE LOOP, WHILE, and REPEAT constructs for flow control within stored programs. MySQL支持IF、CASE、ITERATE、LEAVE LOOP、WHILE和REPEAT构造，用于存储程序中的流控制。It also supports RETURN within stored functions.它还支持在存储函数中使用RETURN。

Many of these constructs contain other statements, as indicated by the grammar specifications in the following sections. 这些构造中的许多都包含其他语句，如下面几节中的语法规范所示。Such constructs may be nested. 这种构造可以嵌套。For example, an IF statement might contain a WHILE loop, which itself contains a CASE statement.例如，IF语句可能包含WHILE循环，WHILE循环本身包含CASE语句。

MySQL does not support FOR loops.MySQL不支持FOR循环。