为什么mysql给出错误"不允许从函数返回结果集"？

Question

我试图使用phpMyAdmin创建一个MySQL函数并得到此错误.

#1415 - Not allowed to return a result set from a function

功能代码如下

DELIMITER $$

CREATE FUNCTION get_binary_count(a INT, c INT)
RETURNS INT
DETERMINISTIC 

BEGIN

DECLARE c1, c2 INT;
SET c1=0;
SET c2=0;

SELECT left_id AS c1 FROM mlm_user_mst WHERE parent_id=a AND left_id>0;
SELECT right_id AS c2 FROM mlm_user_mst WHERE parent_id=a AND right_id>0;

IF(c1>0 AND c2>0)
THEN
SET c=c+1;
SET c=c+get_binary_count(c1,0);
SET c=c+get_binary_count(c2,0);
END IF;

RETURN c;

END$$

DELIMITER ;

有什么建议？

提前致谢

Answer 1

因为

SELECT left_id AS c1 FROM mlm_user_mst WHERE parent_id=a AND left_id>0; 

不设置变量c1,它返回一个名为c1的列的集合

你要

SELECT left_id INTO c1 FROM mlm_user_mst WHERE parent_id=a AND left_id>0; 

同样适用于c2.

Answer 2

这是因为您使用的SELECT查询的输出未存储到变量中或临时存储在FUNCTION必须的内部.函数只能返回一个值.所以你的代码应该是这样的:

CREATE TABLE t1 AS SELECT left_id AS c1 FROM mlm_user_mst WHERE parent_id=a AND left_id>0;
CREATE TABLE t2 AS SELECT right_id AS c2 FROM mlm_user_mst WHERE parent_id=a AND right_id>0;

要么

SELECT left_id AS c1 INTO @c1 FROM mlm_user_mst WHERE parent_id=a AND left_id>0 LIMIT 1; 

SELECT right_id AS c2 INTO @c2 FROM mlm_user_mst WHERE parent_id=a AND right_id>0 LIMIT 1;