[英]SQL Help Inner JOIN LEFT JOIN
我的查詢是:
SELECT Pics.ID, Pics.ProfileID, Pics.Position, Rate.ID as RateID, Rate.Rating, Rate.ProfileID, Gender
FROM Pics
INNER JOIN Profiles ON Pics.ProfileID = Profiles.ID
LEFT JOIN Rate ON Pics.ID = Rate.PicID
WHERE Gender = 'female'
ORDER BY Pics.ID
結果是:
ID ProfileID Position RateID Rating ProfileID Gender
23 24 1 59 9 42 female
24 24 2 33 8 32 female
23 24 1 53 3 40 female
26 24 4 31 8 32 female
30 25 4 30 8 32 female
24 24 2 58 4 42 female
現在,我要執行另一個查詢,即:如果Rate.ProfileID = 32,則刪除任何包含相同Pics.ID的行。
所以留下:
ID ProfileID Position RateID Rating ProfileID Gender
23 24 1 59 9 42 female
23 24 1 53 3 40 female
並刪除所有重復的Pics.ID,因此它們都是23,因此只保留了上述之一:
23 24 1 59 9 42母頭或23 24 1 53 3 40母頭
您可能應該擺脫“神奇數字”,例如32。也就是說,我認為這將為您提供所需的東西。
SELECT
P.ID,
P.ProfileID,
P.Position,
R.ID as RateID,
R.Rating,
R.ProfileID,
PR.Gender
FROM
Pics P
INNER JOIN Profiles PR ON PR.ID = P.ProfileID
LEFT JOIN Rate R ON R.PicID = P.ID
WHERE
PR.Gender = 'female' AND
NOT EXISTS (
SELECT *
FROM Pics P2
INNER JOIN Profiles PR2 ON PR2.ID = P2.ProfileID
INNER JOIN Rate R2 ON R2.PicID = P2.ID AND R2.ProfileID = 32
WHERE
P2.ID = P.ID
)
ORDER BY
P.ID
@Shadow因為第二行包含Rate.ProfileID = 32,並且該Pic.ID = 24,所以它必須刪除所有Pic.ID = 24,這也刪除了底行。
SELECT Pics.ID, Pics.ProfileID, Pics.Position, Rate.ID as RateID, Rate.Rating, Rate.ProfileID, Gender
FROM Pics
INNER JOIN Profiles ON Pics.ProfileID = Profiles.ID
LEFT JOIN Rate ON Pics.ID = Rate.PicID
WHERE Gender = 'female' AND Pics.ID NOT IN (
SELECT Pics.ID
FROM Pics
INNER JOIN Profiles ON Pics.ProfileID = Profiles.ID
LEFT JOIN Rate ON Pics.ID = Rate.PicID
WHERE Gender = 'female' AND Rate.ProfileID = 32)
ORDER BY Pics.ID
嘗試這個:
SELECT Pics.ID, Pics.ProfileID, Pics.Position, Rate.ID as RateID,
Rate.Rating, Rate.ProfileID, Gender
FROM Pics
INNER JOIN Profiles ON Pics.ProfileID = Profiles.ID
LEFT JOIN Rate ON Pics.ID = Rate.PicID
LEFT JOIN Rate AS r
ON Rate.ProfileID = r.ProfileID AND Rate.ID > r.ID
WHERE Gender = 'female' AND (Pics.ProfileID <> 32) AND (r.ID IS NULL)
ORDER BY Pics.ID
最后一個LEFT JOIN
操作使用ON
子句中的此謂詞幫助識別重復項:
Rate.ProfileID = r.ProfileID
如果存在此類重復項(如Rate.ProfileID = 42
的情況),則由於以下條件,僅返回具有最大 Rate.ID
:
Rate.ID > r.ID (`ON` clause)
和
(r.ID IS NULL) (`WHERE` clause)
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