MySQL的左連接方面條件都排連接

Question

我有兩個表，fos_user和區域 與

• fos_user {id，name，enabled}
• zone {id，fos_user_id，enabled}

每個fos_user可以存在多於zone

我需要過濾fos_users僅具有zone與enabled=1

我嘗試用

SELECT * FROM fos_user as u 
LEFT JOIN zona as z ON u.id=z.users_id 
WHERE z.enabled=1 AND u.enabled=1 

，但我得到的fos_user有與enabled=1

幾乎一個區域列表我怎麼能固定？

謝謝

Answer 1

您需要第二個條件來排除未啓用區域中的用戶。

SELECT * 
FROM fos_user AS u 
INNER JOIN zone AS z on u.id = z.users_id 
LEFT JOIN zone AS z1 on u.id = z1.users_id AND z1.enabled = 0 
WHERE u.enabled = 1 AND z.enabled = 1 
AND z1.id IS NULL 

您使用INNER JOIN精確匹配的區域，並使用LEFT JOIN有NULL測試，以找出用戶是不匹配標準（見Return row only if value doesn't exist）。

Answer 2

可以按用戶組，並比較啓用了區域的數量對區的總數：

SELECT * 
    FROM fos_user u 
    JOIN zone z ON u.id = z.users_id 
WHERE u.enabled = 1 
GROUP BY u.id 
HAVING SUM(z.enabled = 1) = COUNT(*);