How to write a loop statement in mysql

Mysql method of writing loop statements: 1. Use a while loop, the code is [WHILE i

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How to write loop statements in mysql:

There are three common looping methods in mysql: while, repeat and loop loops. 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test
BEGIN
DECLARE i INT;  # 申明变量
SET i = 0;  # 变量赋值
WHILE i<5 DO # 结束循环的条件: 当i大于5时跳出while循环
INSERT INTO test VALUES(i+11,&#39;test&#39;,&#39;20&#39;);  # 往test表添加数据
SET i = i+1;    # 循环一次,i加1
END 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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