MYSQL存储过程select语句select不正确的ID

Question

在存储过程方面，我不是最有知识的人，这个问题让我大吃一惊!

基本上我只是想运行一个简单的更新语句，但是当我在过程中运行它时，我选择更新行的用户 ID 不正确，但如果我在过程外运行相同的选择语句，它返回预期结果。

DELIMITER $$
CREATE PROCEDURE catchUpBbs_Users()
  BEGIN
    DECLARE done INT DEFAULT 0;
    DECLARE deleteUser, keepUser VARCHAR(255);
    DECLARE id INT;
    DECLARE cur1 CURSOR FOR SELECT u.username, b.username, b.id from users u RIGHT     JOIN bbs_users b ON u.username = b.username WHERE u.username IS NULL;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;     
    OPEN cur1;
        allusers: LOOP 
            FETCH cur1 INTO keepUser, deleteUser, id;
            IF done THEN 
                LEAVE allusers; 
            END IF;
IF deleteUser != 'anonymous' THEN 

-- This is where the problems start

-- Just for test purposes, returns correct id and username 
SELECT id, username FROM bbs_users WHERE username = deleteUser; 

-- Just for test purposes, return INCORRECT id, but the CORRECT username  
SELECT id, username FROM bbs_users WHERE username = 'anonymous'; 

-- The update statement that does not work as I want it to, sets the user_id to be what it already it, so no updates occur
UPDATE bbs_posts SET user_id = (SELECT id FROM bbs_users WHERE username = 'anonymous') WHERE user_id = (SELECT id FROM bbs_users WHERE username = deleteUser);

-- delete the user from the bbs_users table
DELETE FROM bbs_users WHERE username = deleteUser;

END IF;
    END LOOP allusers;
    CLOSE cur1;
END;

$$
DELIMITER ;

当我调用过程时，两个测试选择语句返回:

1) 这些结果都是正确的

 SELECT id, username FROM bbs_users WHERE username = deleteUser;
 +------+----------+
 | id   | username |
 +------+----------+
 |   13 | deleteme |
 +------+----------+

2)ID不对，但是用户名不对，ID应该是1

 SELECT id, username FROM bbs_users WHERE username = 'anonymous'; 
 +------+-----------+
 | id   | username  |
 +------+-----------+
 |   13 | anonymous |
 +------+-----------+

当我运行相同的，减去变量，过程外的选择语句都返回正确的结果

1) 这些结果都是正确的

SELECT id, username FROM bbs_users WHERE username = 'deleteme';
+----+----------+
| id | username |
+----+----------+
| 13 | deleteme |
+----+----------+

2) 这些结果都是正确的

SELECT id, username FROM bbs_users WHERE username = 'anonymous';
+----+-----------+
| id | username  |
+----+-----------+
|  1 | anonymous |
+----+-----------+

我做错了什么？在使用存储过程时涉及选择和变量时，我是否遗漏了什么？

任何帮助或建议将不胜感激

Answer 1

问题是您在游标中定义了一个名为 id 的标量变量，并且您正在选择它，因此游标内的两个选择语句都使用该存储的标量值对 id 的引用。

为了获得“正确”的值，您需要消除所有歧义:

-- Just for test purposes, returns correct id and username 
SELECT b.id, b.username FROM bbs_users b WHERE b.username = deleteUser; 

-- Just for test purposes, return INCORRECT id, but the CORRECT username  
SELECT b.id, b.username FROM bbs_users b WHERE b.username = 'anonymous';