如何选择主表数据和选择参考表顶部一个数据sql查询

Question

我需要一个sql查询，它应该返回主表项和它的子表项(最新的一个条目仅)。我使用内连接。但是它不能正常工作。谁能给我一个合适的查询这个

Thanks in advance

Answer 1

在SQLServer2005+中使用OUTER APPLY操作符

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

带有CTE和ROW_NUMBER()排序函数的OR选项

;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

试试这个，

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