SQL保持44個外鍵500個最新的項目在一個表中

Question

我有一個表具有以下3列

Recid (primary key), different_recid(foreign key), and details 

我想寫的10項具體different_recids的查詢，刪除那些所有行different_recids只有最近一次除外。

任何人都有建議。

Answer 1

DECLARE @MyTable TABLE 
(
    RecID   INT IDENTITY(1,1) PRIMARY KEY, 
    Different_RecID INT, 
    Create_Date  DATETIME 
); 

INSERT @MyTable (Different_Recid, Create_Date) 
SELECT 1, '20130101' UNION ALL 
SELECT 1, '20130102' UNION ALL 
SELECT 1, '20130103' UNION ALL 

SELECT 2, '20130211' UNION ALL 
SELECT 2, '20130212' UNION ALL 

SELECT 3, '20130102' UNION ALL 
SELECT 3, '20130103'; 

DECLARE @RowsToDelete TABLE(ID INT PRIMARY KEY); 
INSERT @RowsToDelete VALUES (1); 
INSERT @RowsToDelete VALUES (2); 

DELETE [Target] 
-- OUTPUT deleted.* -- <-- Uncomment this line to see deleted rows 
FROM 
(
    SELECT * 
    FROM 
    (
     SELECT ROW_NUMBER() OVER(PARTITION BY x.Different_RecID ORDER BY x.Create_Date DESC) RowNum, x.* 
     FROM @MyTable x 
     WHERE EXISTS 
     ( 
      SELECT * 
      FROM @RowsToDelete d 
      WHERE x.Different_RecID = d.ID 
     ) 
    ) src 
    WHERE src.RowNum > 1 
) AS [Target]; 

結果：

SELECT * FROM @MyTable; 
/* 
RecID Different_RecID Create_Date 
----- --------------- ----------- 
3  1    2013-01-03 
5  2    2013-02-12 
6  3    2013-01-02 
7  3    2013-01-03 
*/