Question

我用多个CTE编写一个查询，从第一个CTE中选择所有行，从第二个CTE中选择4行。我选择了部分，但它返回CTE2中的整个项目。

this is what it returns and selected part that i want.

这是我的查询：

;WITH CTE1(UserName, ItemId, ItemName, ImageId, ImageName) AS
    (
        SELECT [Users].UserName, [Items].ItemId, [Items].Name, [Images].ImageId, [Images].Name
            FROM Items INNER JOIN Images
                ON [Items].ItemId = [Images].ItemId INNER JOIN Users
                    ON [Items].UserId = TestUser.UserId
        WHERE ([Items].ItemId = 1) AND ([Items].UserId = 1) AND ([Items].Name = N'Pen')
    ),
CTE2(ItemId, ItemName, ImageId, ImageName) AS
    (
        SELECT [Items].ItemId, [Items].Name, [Images].ImageId, [Images].Name
            FROM Items INNER JOIN [Images]
                ON [Items].ItemId = [Images].ItemId
            WHERE [Items].UserId = 1
        GROUP BY [Items].ItemId, [Items].Name, [Images].ImageId, [Images].Name
    )
SELECT CTE1.UserName, CTE1.ItemId AS ItemId1, CTE1.ItemName AS ItemName1,
    CTE1.ImageId AS ImageId1, CTE1.ImageName AS ImageName1, COUNT(CTE1.ItemId) OVER() AS ItemCounter1,
        CTE2.ItemId AS ItemId2, CTE2.ItemName AS ItemName2, CTE2.ImageId AS ImageId2, CTE2.ImageName AS ImageName2, COUNT(CTE2.ItemId) OVER() AS TotalCount
FROM (SELECT *, ROW_NUMBER() OVER(PARTITION BY ItemId ORDER BY ItemId) AS RN FROM CTE2) CTE2 LEFT JOIN CTE1
    ON CTE2.ItemId = CTE1.ItemId WHERE RN = 1 ORDER BY CTE1ItemId DESC

所有帮助都将得到赞赏。

Answer 1

我不确切地知道你想要什么或者哪四行，但TOP 4会浮现在脑海中：

WITH CTE1(UserName, ItemId, ItemName, ImageId, ImageName) AS (
      SELECT TOP 4 [Users].UserName, [Items].ItemId, [Items].Name, [Images].ImageId, [Images].Name
      FROM Items INNER JOIN
           Images
           ON [Items].ItemId = [Images].ItemId INNER JOIN
           Users
           ON [Items].UserId = TestUser.UserId
      WHERE ([Items].ItemId = 1) AND ([Items].UserId = 1) AND ([Items].Name = N'Pen')
    ),
    . . .

通常情况下，会有ORDER BY来选择最近的四个，最旧的四个，最红的四个或其他。

Answer 2

感谢您的帮助。

我再次写了我的查询，得到了我的错。我知道这不是一件平常的事情，但我想与其他可能有这个问题的人分享我的问题。

这就是我写的：


    WITH CTE1(ItemId, ItemName, Category, UserId, Created, ImageId, ImageName) AS
    (
    SELECT [Items].ItemId, [Items].Name, [Items].CategoryId, [Items].UserId, [Items].Created, [Images].ImageId, [Images].Name
        FROM [Items] INNER JOIN [Images]
    ON [Items].ItemId = [Images].ItemId
    WHERE ([Items].UserId = 1) AND ([Items].ItemId = 1) AND ([Items].Name = N'Kolah')
    GROUP BY [Items].ItemId, [Items].Name, [Items].CategoryId, [Items].UserId, [Items].Created, [Images].ImageId, [Images].Name
    ),
    CTE2(ItemId, ItemName, Category, UserId, Created, ImageId, ImageName) AS
    (
    SELECT [Items].ItemId, [Items].Name, [Items].CategoryId, [Items].UserId, [Items].Created, [Images].ImageId, [Images].Name
        FROM [Items] INNER JOIN [Images]
    ON [Items].ItemId = [Images].ItemId
    WHERE ([Items].UserId = 1)
    GROUP BY [Items].ItemId, [Items].Name, [Items].CategoryId, [Items].UserId, [Items].Created, [Images].ImageId, [Images].Name
    )
    SELECT TOP 4 CTE2.ItemId, CTE2.ItemName, CTE2.Category, CTE2.UserId, CTE2.Created, CTE2.ImageId, CTE2.ImageName
        FROM (SELECT *, ROW_NUMBER() OVER(PARTITION BY ItemId ORDER BY ItemId) AS RN FROM CTE2) CTE2
    WHERE RN = 1
        UNION
    SELECT CTE1.ItemId, CTE1.ItemName, CTE1.Category, CTE1.UserId, CTE1.Created, CTE1.ImageId, CTE1.ImageName
        FROM CTE1
    ORDER BY ItemId DESC

非常感谢。

如何在多个CTE中从第二个CTE中选择前n行

2 个答案: