如何選擇主表數據並選擇參考表頂部的一個數據sql查詢

Question

我需要一個sql查詢，它應該返回主表項和它的子表項（最新的一個條目只有）。我爲此使用了內連接。但我沒有正常工作。 誰能給一個給我這個

得益於正確的查詢提前

Answer 1

在SQLServer2005的+與OUTER APPLY操作

SELECT * 
FROM master t1 OUTER APPLY (
          SELECT TOP 1 t2.Col1, t2.Col2 ... 
          FROM child t2 
          WHERE t1.Id = t2.Id 
          ORDER BY t2.CreatedDate DESC 
          ) o 

或選項使用選項與CTE和ROW_NUMBER()排名功能

;WITH cte AS 
(       
    SELECT *, 
     ROW_NUMBER() OVER(PARTITION BY t1.Id ORDER BY t2.CreatedDate DESC) AS rn 
    FROM master t1 JOIN child t2 ON t1.Id = t2.Id 
) 
    SELECT * 
    FROM cte 
    WHERE rn = 1 

Answer 2

試試這個，

SELECT ID, DATE 
(
SELECT M.ID, C.DATE, ROW_NUMBER() OVER(PARTITION BY M.ID ORDER BY C.DATE DESC) RN 
FROM MASTER M 
JOIN CHILD C 
ON C.ID = M.ID 
) A 
WHERE RN = 1