sql - 在一列上选择 DISTINCT

Question

使用 SQL Server，我有...

ID  SKU     PRODUCT
=======================
1   FOO-23  Orange
2   BAR-23  Orange
3   FOO-24  Apple
4   FOO-25  Orange

我想

1   FOO-23  Orange
3   FOO-24  Apple

这个查询没有让我到达那里。如何仅在一列上 SELECT DISTINCT？

SELECT 
[ID],[SKU],[PRODUCT]
FROM [TestData] 
WHERE ([PRODUCT] = 
(SELECT DISTINCT [PRODUCT] FROM [TestData] WHERE ([SKU] LIKE 'FOO-%')) 
ORDER BY [ID]

Answer 1

假设您使用的是 SQL Server 2005 或更高版本，您可以将 CTE 与 ROW_NUMBER() 一起使用：

SELECT  *
FROM    (SELECT ID, SKU, Product,
                ROW_NUMBER() OVER (PARTITION BY PRODUCT ORDER BY ID) AS RowNumber
         FROM   MyTable
         WHERE  SKU LIKE 'FOO%') AS a
WHERE   a.RowNumber = 1

Answer 2

最简单的解决方案是使用子查询来查找与您的查询匹配的最小 ID。在您使用的子查询中，GROUP BY而不是DISTINCT：

SELECT * FROM [TestData] WHERE [ID] IN (
   SELECT MIN([ID]) FROM [TestData]
   WHERE [SKU] LIKE 'FOO-%'
   GROUP BY [PRODUCT]
)

Answer 3

尝试这个：

SELECT 
    t.*
    FROM TestData t
        INNER JOIN (SELECT
                        MIN(ID) as MinID
                        FROM TestData
                        WHERE SKU LIKE 'FOO-%'
                   ) dt ON t.ID=dt.MinID

编辑
一旦 OP 更正了他的示例输出（以前只有一个结果行，现在已全部显示），这是正确的查询：

declare @TestData table (ID int, sku char(6), product varchar(15))
insert into @TestData values (1 ,  'FOO-23'      ,'Orange')
insert into @TestData values (2 ,  'BAR-23'      ,'Orange')
insert into @TestData values (3 ,  'FOO-24'      ,'Apple')
insert into @TestData values (4 ,  'FOO-25'      ,'Orange')

--basically the same as @Aaron Alton's answer:
SELECT
    dt.ID, dt.SKU, dt.Product
    FROM (SELECT
              ID, SKU, Product, ROW_NUMBER() OVER (PARTITION BY PRODUCT ORDER BY ID) AS RowID
              FROM @TestData
              WHERE  SKU LIKE 'FOO-%'
         ) AS dt
    WHERE dt.RowID=1
    ORDER BY dt.ID

Answer 4

SELECT min (id) AS 'ID', min(sku) AS 'SKU', Product
    FROM TestData
    WHERE sku LIKE 'FOO%' -- If you want only the sku that matchs with FOO%
    GROUP BY product 
    ORDER BY 'ID'

Answer 5

我知道 6 年前有人问过这个问题，但知识仍然是知识。这是与上述不同的解决方案，因为我必须在 SQL Server 2000 下运行它：

DECLARE @TestData TABLE([ID] int, [SKU] char(6), [Product] varchar(15))
INSERT INTO @TestData values (1 ,'FOO-23', 'Orange')
INSERT INTO @TestData values (2 ,'BAR-23', 'Orange')
INSERT INTO @TestData values (3 ,'FOO-24', 'Apple')
INSERT INTO @TestData values (4 ,'FOO-25', 'Orange')

SELECT DISTINCT  [ID] = ( SELECT TOP 1 [ID]  FROM @TestData Y WHERE Y.[Product] = X.[Product])
                ,[SKU]= ( SELECT TOP 1 [SKU] FROM @TestData Y WHERE Y.[Product] = X.[Product])
                ,[PRODUCT] 
            FROM @TestData X  

Answer 6

这是一个版本，与其他几个答案基本相同，但是由于一些内联值，您可以将粘贴复制到 SQL Server Management Studio 中进行测试（并且不会生成任何不需要的表）。

WITH [TestData]([ID],[SKU],[PRODUCT]) AS
(
    SELECT *
    FROM (
        VALUES
        (1,   'FOO-23',  'Orange'),
        (2,   'BAR-23',  'Orange'),
        (3,   'FOO-24',  'Apple'),
        (4,   'FOO-25',  'Orange')
    )
    AS [TestData]([ID],[SKU],[PRODUCT])
)

SELECT * FROM [TestData] WHERE [ID] IN 
(
    SELECT MIN([ID]) 
    FROM [TestData] 
    GROUP BY [PRODUCT]
)

结果

ID  SKU     PRODUCT
1   FOO-23  Orange
3   FOO-24  Apple

我忽略了以下...

WHERE ([SKU] LIKE 'FOO-%')

作为作者错误代码的唯一部分，而不是问题的一部分。这不太可能对看这里的人有帮助。

Answer 7

尝试这个：

SELECT * FROM [TestData] WHERE Id IN(SELECT DISTINCT MIN(Id) FROM [TestData] GROUP BY Product)