mysql游标 循环_MySQL游标与嵌套循环

游标嵌套遍历

user表：

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`()

BEGIN

DECLARE user1 VARCHAR(100);

DECLARE user2 VARCHAR(100);

DECLARE done INT DEFAULT 0;

DECLARE cursor_user1 CURSOR FOR(SELECT `name` FROM `user`); -- 定于游标1

DECLARE cursor_user2 CURSOR FOR(SELECT `name` FROM `user`); -- 定义游标2

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; -- 结束标识

OPEN cursor_user1; -- 开启游标1

loop_1: LOOP -- 外层循环

-- -------------------------------------------------------------------------------------

# 尝试从游标1指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。

FETCH cursor_user1 INTO user1;

IF done = 1 THEN LEAVE loop_1; END IF; -- 外层循环结束条件

OPEN cursor_user2; -- 开启游标2

loop_2: LOOP -- 内层循环

-- -----------------------------------------------------------------------------

# 尝试从游标2指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。

FETCH cursor_user2 INTO user2;

IF done = 1 THEN LEAVE loop_2; END IF; -- 内层循环结束条件

# do something...

-- -----------------------------------------------------------------------------

END LOOP loop_2;

CLOSE cursor_user2; -- 关闭游标2

SET done = 0; -- important

-- ------------------------------------------------------------------------------------

END LOOP loop_1;

CLOSE cursor_user1; -- 关闭游标1

END

测试

user表数据：

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`()

BEGIN

DECLARE result VARCHAR(2000) DEFAULT 'result';

DECLARE user1 VARCHAR(100);

DECLARE user2 VARCHAR(100);

DECLARE done INT DEFAULT 0;

DECLARE cursor_user1 CURSOR FOR(SELECT `name` FROM `user`); -- 定于游标1

DECLARE cursor_user2 CURSOR FOR(SELECT `name` FROM `user`); -- 定义游标2

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; -- 结束标识

OPEN cursor_user1; -- 开启游标1

loop_1: LOOP -- 外层循环

-- -------------------------------------------------------------------------------------

# 尝试从游标1指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。

FETCH cursor_user1 INTO user1;

IF done = 1 THEN LEAVE loop_1; END IF; -- 外层循环结束条件

OPEN cursor_user2; -- 开启游标2

loop_2: LOOP -- 内层循环

-- -----------------------------------------------------------------------------

# 尝试从游标2指向的数据集合获取数据，如果集合已经遍历完毕，done的值被设置为1。

FETCH cursor_user2 INTO user2;

IF done = 1 THEN LEAVE loop_2; END IF; -- 内层循环结束条件

# do something...

SET result = CONCAT(result,';',user1,'-',user2);

-- -----------------------------------------------------------------------------

END LOOP loop_2;

CLOSE cursor_user2; -- 关闭游标2

SET done = 0; -- important

-- ------------------------------------------------------------------------------------

END LOOP loop_1;

CLOSE cursor_user1; -- 关闭游标1

SELECT result;

END

执行结果：