SQL在左聯接中使用內部查詢

Question

我有下面的兩個表一和二

ONE           TWO

ID            ID  CODE  
-----         ---------
1             1    1
2             1    2
3             2    1
4             3    1  
5             3    2  
              3    3

需要輸出

ID    CODE  
----------  
1     2  
2     1  
3     3  
4     NULL  
5     NULL  

我使用了以下查詢，但引發了錯誤“ 與JOIN運算符或MERGE語句關聯的ON子句無效。 ”

SELECT  A.ID
       ,B.CODE
FROM   ONE A 
LEFT JOIN
       TWO B
ON     A.ID = B.ID
   AND B.CODE = (
                   SELECT 
                         MAX(Z.CODE)
                   FROM TWO Z
                   WHERE Z.ID = A.ID
            )

Answer 1

您可以使用聯接和聚合來完成此操作（如果我正確理解了邏輯）：

select ONE.id, max(TWO.CODE)
from ONE left outer join
     TWO
     on ONE.id = TWO.id
group by ONE.id;

Answer 2

由於還標記了SQL Server，因此可以使用ROW_NUMBER ：

WITH CTE AS
(
    SELECT ONE.ID,  TWO.CODE,
        RN = ROW_NUMBER() OVER (PARTITION BY ONE.ID ORDER BY TWO.CODE DESC)
    FROM ONE LEFT OUTER JOIN TWO
        ON ONE.ID=TWO.ID
)
SELECT  ID, CODE FROM CTE WHERE RN = 1

演示

Answer 3

SELECT  A.ID
   ,B.CODE
FROM   ONE A 
LEFT outer JOIN
   (select id,max(code) CODE from two group by id) B
ON     A.ID = B.ID

我相信這就是您要尋找的...