循环语句必须在begin end 语句体中

---

循环语句类型

• while
• loop
• repeat

循环控制

• iterate
  类似于java的continue，结束当前循环，继续下一次循环
• leave
  类似于java中的break，结束当前结构体的循环

while循环

结构1

while 循环条件 do
循环体;
end while;

结构2

标签: while 循环条件 do
循环体;
end while 标签;

example

delimiter $
create procedure test_while(IN addCount INT)
begin
    declare i int default 1;
    while i <= addCount
        do
            insert into t_test(user_name, user_age)
            values (concat('name', i), i);
            set i = i + 1;
        end while;
end $

set @counts = 100;
call test_while(@counts);

带IF条件

truncate table t_test;
drop procedure if exists test_while;
delimiter $
create procedure test_while(IN addCount INT)
begin
    declare i int default 1;
    while i <= addCount
        do
            if i > 50 then
                insert into t_test(user_name, user_age)
                values (concat('老三', i), i);
            else
                insert into t_test(user_name, user_age)
                values (concat('老大', i), i);
            end if;
            set i = i + 1;
        end while;
end $

set @counts = 100;
call test_while(@counts);

使用leave控制语句

truncate table t_test;
drop procedure if exists test_while;
delimiter $
create procedure test_while(IN addCount INT)
begin
    declare i int default 1;
    addwx: while i <= addCount
        do
            if i > 50 then
                leave addwx;
            else
                insert into t_test(user_name, user_age)
                values (concat('name', i), i);
            end if;
            set i = i + 1;
        end while addwx;
end $

set @counts = 100;
call test_while(@counts);

使用iterate,i为偶数时写入数据

truncate table t_test;
drop procedure if exists test_while;
delimiter $
create procedure test_while(IN addCount INT)
begin
    declare i int default 1;
    addwx:
    while i <= addCount
        do
            set i = i + 1; bvv 
            if i % 2 = 1 then
                iterate addwx;
            else
                insert into t_test(user_name, user_age)
                values (concat('name', i), i);
            end if;

        end while addwx;
end $

set @counts = 100;
call test_while(@counts);

loop循环 （常用语模拟死循环场景）

标签: loop
循环体;
end loop 标签;

repeat循环

标签： repeat
循环体;
until 结束循环的条件;
end repeat 标签;