選擇獨特的領域

Question

我有這個表：

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

我需要隨機與SELECT TOP 5 ID, Name FROM TableA 與名稱必須是5個記錄中是唯一的提取。

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 

但每次我有完全一樣的結果。

我需要隨機選擇ID的所有值，確保每個記錄的名稱始終不同。

我希望問題是可以理解的。有任何想法嗎？

找到了解決辦法。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

也許問題是，雖然newid()是隨機的，可能往往是連續的。這是否解決了這個問題？

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]