Question

我有这个问题：

SELECT Auctions.ID 
FROM Auctions
INNER JOIN Products ON Auctions.ProductID = Products.ID

据我所知，如果我有拍卖会：

ID | ProductID
1  |   12

ProductID 12不在Products表中，因此不会选择该行。

如果我是对的，我想删除在Products表上找不到产品ID的所有行。（无法找到JOIN的产品）

我该怎么做？

Answer 1

DELETE FROM a
    FROM Auctions a
    WHERE NOT EXISTS(SELECT NULL FROM Products p WHERE p.ID = a.ProductID)

Answer 2

DELETE Auctions WHERE ProductId NOT IN(SELECT ProductId FROM Products)

当然，执行此操作后，如果您不想再次执行此操作，请自行帮助并创建从Auctions.ProductId到Products.ProductId的关系。

Answer 3

对上述答案略有不同。第一个显示拍卖没有相应的产品，第二个实际清除它们。如果存在缺失产品的模式，首先可能会有所帮助。

-- This query identifies everything that is in
-- Auctions that doesn't have a match in Product
SELECT
    A.*
FROM
    Auctions A
    LEFT OUTER JOIN 
        Products P 
        ON A.ProductID = P.ID
WHERE
    P.ProductID IS NULL


-- This query deletes everything that is in
-- Auctions that doesn't have a match in Product
DELETE
    A
FROM
    Auctions A
    LEFT OUTER JOIN 
        Products P 
        ON A.ProductID = P.ID
WHERE
    P.ProductID IS NULL

Answer 4

DELETE FROM Auctions WHERE ProductId NOT IN (SELECT ProductId FROM Products)

删除所有找不到JOIN的行？

4 个答案: