选择唯一字段

Question

我有这张桌子：

TableA
----------------
ID (pk)   Name
1         A
2         B
3         C
4         A
5         D
6         A
7         B
8         A
9         D
10        C
....

我需要用SELECT TOP 5 ID, Name FROM TableA随机提取 使用名称在5条记录中必须是唯一的。

我正在尝试：

;WITH group
AS
(
    SELECT  ID, Name,
            ROW_NUMBER() OVER (PARTITION BY Name ORDER BY NewId()) rn
    FROM    TableA
)
SELECT ID, Name
FROM group
WHERE rn = 1

但每次我都有相同的结果。

我需要随机选择ID的所有值，确保每个记录的名称始终不同。

我希望这个问题是可以理解的。有什么想法吗？

找到解决方案。它似乎工作！

;WITH group 
AS ( 
SELECT ID, Name, ROW_NUMBER() OVER (PARTITION BY Name ORDER BY NewId()) rn FROM TableA ) 
SELECT top 5 ID, Name, NewId() [NewId] 
FROM group 
WHERE rn = 1 
ORDER BY [newid]

Answer 1

问题可能是虽然newid()是随机的，但它可能是顺序的。这样可以解决问题吗？

WITH g as (
      SELECT ID, Name,
             ROW_NUMBER() OVER (PARTITION BY Name ORDER BY RAND(CHECKSUM(NewId()))) as rn
      FROM TableA
     )
SELECT ID, Name
FROM g
WHERE rn = 1;

Answer 2

CREATE TABLE #test(ID INT ,Name VARCHAR(1)) INSERT INTO #test(ID ,Name )
SELECT 1,'A' UNION ALL SELECT 2,'B' UNION ALL SELECT 3,'C' UNION ALL 
SELECT 4,'A' UNION ALL SELECT 5,'D'UNION ALL SELECT 6,'A' UNION ALL
SELECT 7,'B' UNION ALL SELECT 8,'A'UNION ALL SELECT 9,'D' UNION ALL
SELECT 10,'C'

SELECT T1.ID ,T1.Name FROM  #test T1
JOIN ( SELECT TOP 5 Name FROM #test T2 ORDER BY NEWID()
) A ON T1.Name = A.Name ORDER BY A.Name

Answer 3

;WITH group
AS
(
    SELECT  ID, Name,
            ROW_NUMBER() OVER (PARTITION BY Name ORDER BY NewId()) rn
    FROM    TableA
)
SELECT top 5 ID, Name, NewId() [NewId]
FROM group
WHERE rn = 1
ORDER BY [newid]