影響刪除的MySQL存儲過程變量名稱

Question

我遇到了一個MySQL存儲過程非常有趣的問題。其過程如下：

DROP PROCEDURE IF EXISTS `removeSubscription`; 
DELIMITER ;; 
CREATE DEFINER=`root`@`%` PROCEDURE `removeSubscription`(IN `userId` int,IN `channelId` int,IN `channelTypeTitle` varchar(255)) 

BEGIN 

SET @userId = userId; 
SET @channelId = channelId; 
SET @channelTypeTitle = channelTypeTitle; 

DELETE FROM subscriptions 
WHERE 
    userid = @userId AND 
    channelid = @channelId AND 
    channeltypeid = (SELECT id FROM channeltypes WHERE `name` = @channelTypeTitle) 
LIMIT 1; 

END 
;; 
DELIMITER ; 

當這個被稱爲存儲過程從PHP，是忽略所有的「WHERE子句中，並簡單地刪除它遇到的第一行。這意味着，當「LIMIT 1」冷落，它刪除一切從表：■

這是PHP：

$stmt = $db->prepare("CALL removeSubscription(:userId, :channelId, :channelTypeTitle)"); 

$stmt->bindValue('userId', $userId); 
$stmt->bindValue('channelId', $channelId); 
$stmt->bindValue('channelTypeTitle', $channelTypeTitle); 

$stmt->execute(); 

奇怪的是，如果我在PHP都的重命名傳遞的參數準備並在存儲過程中（例如，在它們之前有一個'x'），那麼它就可以正常工作。我在這裏錯過了很明顯的東西嗎

Answer 1

不重用變量名的名稱在它們的作用域內應該是唯一的......並且不要在存儲過程中使用全局變量（它們具有全局作用域，因此您應該使用本地變量） ...

DROP PROCEDURE IF EXISTS `removeSubscription`; 
DELIMITER ;; 
CREATE DEFINER=`root`@`%` PROCEDURE `removeSubscription`(IN `userId` int,IN `channelId` int,IN `channelTypeTitle` varchar(255)) 

BEGIN 

declare userId_, channelId_, channelTypeTitle_ integer; 

SET userId_ = userId; 
SET channelId_ = channelId; 
SET channelTypeTitle_ = channelTypeTitle; 

DELETE FROM subscriptions 
WHERE 
    userid = userId_ AND 
    channelid = channelId_ AND 
    channeltypeid = (SELECT id FROM channeltypes WHERE `name` = channelTypeTitle_) 
LIMIT 1; 

END 
;; 
DELIMITER ;