选择独特的领域

Question

我有这个表：

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

我需要随机与SELECT TOP 5 ID, Name FROM TableA 与名称必须是5个记录中是唯一的提取。

我想：

;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 

但每次我有完全一样的结果。

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。

我希望问题是可以理解的。有任何想法吗？

找到了解决办法。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

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 2

也许问题是，虽然newid()是随机的，可能往往是连续的。这是否解决了这个问题？

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 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]