爲什麼mysql給出錯誤「不允許從函數返回結果集」？

Question

我正在嘗試使用phpMyAdmin創建一個MySQL函數並獲取此錯誤。

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

的功能代碼如下

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 ; 

有什麼建議？

在此先感謝

Answer 1

因爲

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

不設置變量C1，它返回一組與一個名爲列c1

你想

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

同樣爲c2。

Answer 2

這是因爲您正在使用SELECT查詢的輸出未存儲到變量中或臨時存在FUNCTION必須。函數只能返回一個值。所以，你的代碼應該是這樣的：

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; 

或

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;