使用與MySQL

Question

EXISTS我已經不再需要其他所有數據庫系統的工作原理，但無法與MySQL這個簡單的查詢：

UPDATE points p 
SET p.userid = 5224 
WHERE p.userid = 2532 
AND NOT EXISTS (
    SELECT 1 
    FROM points q 
    WHERE q.userid = 5224 
    AND q.game = p.game 
) 

我收到以下錯誤信息：

#1093 - You can't specify target table 'p' for update in FROM clause 

有任何解決方法？

Answer 1

您不能在UPDATE子句中將主表別名化。這應該工作：

UPDATE points 
SET userid = 5224 
WHERE userid = 2532 
AND NOT EXISTS (
    SELECT 1 
    FROM points q 
    WHERE q.userid = 5224 
    AND q.game = points.game 
) 

Answer 2

用途：

UPDATE POINTS 
    SET userid = 5224 
WHERE userid = 2532 
    AND game NOT IN (SELECT q.game 
         FROM POINTS q 
        WHERE q.userid = 5224)