如何选择主表数据并选择referance表顶部的一个数据sql查询

Question

i need an sql query which should return the master table entry and its child table entry ( the latest one entry only ). I used inner join for this. But i its not working fine. Can anyone give a give me a proper query for this

Thanks in advance

Answer 1

In SQLServer2005+ use option with OUTER APPLY operator

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

OR option with CTE and ROW_NUMBER() ranking function

;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

Try this,

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