（1）IF语句
IF search_condition THEN statement_list
[ELSEIF search_condition THNE statement_list]
[ELSE statement_list]
END IF
（2）CASE语句
CASE case_value
WHEN when_value THEN statement_list
[WHEN when_value THEN statement_list]...
[ELSE statement_list]
END CASE
或者
CASE
WHEN search_conditon THEN statement_llist
[WHEN search_condition THEN statement_list]...
[ELSE statement_list]
END CASE
例句：
case
when i_staff_id =2 then
set @x1=@x1+d_amount;
else
set @x2=@x2+d_amount;
end case;
（3）Loop
[begin_label:] Loop
statement_list
END LOOP [end_label]
（4）LEAVE语句
用于从标注的流程构造中退出
示例：
CREATE PROCEDURE actor_insert()
BEGIN
set @x=0;
ins : LOOP
set @x = @x +1 ;
IF @x= 100 then
leave ins;
END IF;
INSERT INTO actor(first_name,last_name) VALUES ('TEST','201');
END LOOP ins;
END ;
$$
（5）ITERATE 语句
该语句必须用在循环中，作用是跳过当前循环的剩下的语句，直接进入下一轮循环。
CREATE PROCEDURE actor_insert()
BEGIN
set @x=0;
ins: LOOP
set @x=@x+1;
IF @x=10 then
leave ins;
ELSEIF mod(@x,2)=0 then
ITERATE ins;
END IF;
INSERT INTO actor(actor_id,first_name,last_name) VALUES (@x+200 , 'Test', @x);
END LOOP ins;
end;
(6) REPEAT 语句
[begin_label:] REPEAT
statement_list
UNTIL search_condition
END REPEAT [end_label]
示例：
REPEAT
FETCH cur_payment INTO i_staff_id,d_amount;
if i_staff_id =2 then
set @x1=@x1 + d_amount;
else
set @x2=@x2 + d_amount;
end if;
UNTIL 0 END REPEAT;
（7）WHERE语句
[begin_label:]WHILE search_condition DO
statement_list
END WHILE [end_label]
示例：
CREATE PROCEDURE loop_demo()
BEGIN
set @x=1 ,@x1=1;
REPEAT
set @x=@x+1;
UNTIL @x> 0 end repeat;
while @x1<0 do
set @x1=@x1 +1;
end while;
END;