What are the loop statements in MySQL?

There are three commonly used looping methods in MySQL: while, repeat and loop.． There is also a kind of goto, which is not recommended.

1.while loop

-- 设置mysql分隔符为//，也就意味着，当遇到下一个//时，整体执行SQL语句
DELIMITER //

DROP PROCEDURE if EXISTS ‘test’;    # 如果存在test存储过程则删除CREATE procedure test() # 创建无参存储过程，名称为testBEGIN
DECLARE i INT;  # 申明变量SET i = 0;  # 变量赋值WHILE i# 结束循环的条件: 当i大于5时跳出while循环
INSERT INTO test VALUES(i+11,'test','20');  # 往test表添加数据SET i = i+1;    # 循环一次,i加1END WHILE;  # 结束while循环SELECT * FROM test; # 查看test表数据END
//  # 结束定义语句CALL test();    # 调用存储过程DELIMITER ; # 重新将分隔符设置为;

2.repeat loop

DELIMITER //
DROP PROCEDURE IF EXISTS test;
CREATE PROCEDURE test()
BEGIN
 DECLARE i INT;
 SET i = 0;
 REPEAT
   INSERT INTO test VALUES(i+11,'test','20');           # 往test表添加数据   SET i = i + 1;                                  # 循环一次,i加一 UNTIL i > 10 END REPEAT;                           # 结束循环的条件: 当i大于10时跳出repeat循环 SELECT * FROM test;
END
//
CALL test();
DELIMITER ;

3.loop loop

DELIMITER //
DROP PROCEDURE IF EXISTS test;
CREATE PROCEDURE test()
BEGIN
 DECLARE i INT;
 SET i = 0;
   lp : LOOP                                   # lp为循环体名,可随意 loop为关键字       INSERT INTO test VALUES(i+11,'test','20');   # 往test表添加数据       SET i = i + 1;                          # 循环一次,i加一       IF i > 10 THEN                       # 结束循环的条件: 当i大于10时跳出loop循环                   LEAVE lp;
           END IF;
   END LOOP;
   SELECT * FROM test;
END
//
CALL test();
DELIMITER ;

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