mysql在使用NOT IN條件時左連接兩個表

Question

我想在使用mysql「NOT IN」條件時連接兩個表。我遇到的問題是，如果左連接爲空，意味着沒有進入左連接，則mysql NOT IN運算符不起作用。

這裏是一個例子。

SELECT PLAYERS.*, 
TYPES.GUEST_ID 

FROM PLAYERS 
LEFT JOIN TYPES ON TYPES.GUEST_ID = PLAYERS.GUEST_ID 
WHERE PLAYERS.ID = '1' AND TYPES.GUEST_ID NOT IN('1', '2') 

由於TYPES表中目前沒有匹配的行。 NOT IN運算符不起作用。有沒有解決方法？

Answer 1

使用IS NULL在：

SELECT PLAYERS.*, TYPES.GUEST_ID 
FROM PLAYERS 
    LEFT JOIN TYPES ON TYPES.GUEST_ID = PLAYERS.GUEST_ID 
WHERE TYPES.GUEST_ID NOT IN('1', '2') OR TYPES.GUEST_ID IS NULL 

Answer 2

把它放在on條款

SELECT PLAYERS.*, 
TYPES.GUEST_ID 
FROM PLAYERS 
LEFT JOIN TYPES ON TYPES.GUEST_ID = PLAYERS.GUEST_ID 
       AND TYPES.GUEST_ID NOT IN(1, 2)