MAX函数没有返回最大值，返回的所有值，而不是

Question

我有User_Transfer的表看起来像下面

ID User_ID User_No Date_From Date_To 
1  00001 KJH789 2014-04-26 2014-04-29 
2  00001 KJH789 2014-04-01 2014-04-04 
3  00004 TGI567 2014-04-26 2014-04-29 
4  00026 RTW763 2014-04-09 2014-04-12 

和表User_Profile

ID User_ID User_Name Nationality_Code 
1  00001  John  JAP 
2  00004  Sarah  SG 
3  00026  Timmy  SG 

我的查询：

SELECT X.USER_ID, 
      X.USER_NO, 
      X.USER_NAME, 
      X.NATIONALITY_CODE, 
      U.DATE_FROM, 
      X.DATE_TO 
    FROM 
    (SELECT 
     ID, 
     USER_ID, 
     USER_NO, 
    (SELECT EB.USER_NAME FROM USER_PROFILE EB WHERE EB.USER_ID = USER_TRANSFER.USER_ID) AS USER_NAME, 
    (SELECT EB.NATIONALITY_CODE FROM USER_PROFILE EB WHERE EB.USER_ID = USER_TRANSFER.USER_ID) AS NATIONALITY_CODE 
    MAX(DATE_TO) AS DATE_TO 
    FROM USER_TRANSFER 
    GROUP BY 
     ID, 
     USER_ID, 
     USER_NO, 
     EMPLOYEE_NO) X, 
    USER_TRANSFER U 
    WHERE 
    U.ID = X.ID AND 
    U.USER_ID = X.USER_ID 
    ORDER BY X.USER_NO 

我上面的查询返回了4条记录，而不是3条。
我试过t Ø得到看起来像下面的结果：

User_ID User_No User_Name Nationality_Code Date_From Date_To 
    00001 KJH789  John  JAP    2014-04-26 2014-04-29 
    00004 TGI567  Sarah  SG    2014-04-26 2014-04-29 
    00026 RTW763  Timmy  SG    2014-04-09 2014-04-12 

Answer 1

不要把ID列在GROUP BY这就是为什么你会得到所有行， 所以试试下面的查询

SELECT X.USER_ID, 
     X.USER_NO, 
     EB.USER_NAME, 
     EB.NATIONALITY_CODE, 
     x.DATE_FROM, 
     X.DATE_TO 
FROM 
(SELECT USER_ID,USER_NO,Max(DATE_From) AS DATE_From, MAX(DATE_TO) AS DATE_TO 
    FROM USER_TRANSFER 
    GROUP BY USER_ID,USER_NO) X 
left join USER_ID EB on x.USER_ID=EB.USER_ID 

ORDER BY X.USER_NO 

Answer 2

你可以参考我的解决方案：

SELECT  Uf.USER_ID, 
      Uf.USER_NO, 
      Upro.USER_NAME, 
      Upro.NATIONALITY_CODE, 
      Uf.DATE_FROM, 
      T1.DATE_TO 
    FROM User_Transfer as Uf 
JOIN (Select USER_ID, 
     USER_NO, 
     MAX(Date_to) AS Date_To 
     FROM User_Transfer 
     GROUP BY USER_ID, USER_NO) as T1 --get all user_id and user_no that have max date_to 
ON T1.USER_ID = Uf.USER_ID AND T1.USER_NO = Uf.USER_NO 
          AND T1.Date_To = Uf.Date_To 
JOIN User_Profile AS Upro 
ON Upro.USER_ID = Uf.USER_ID 

Answer 3

尝试：

http://www.sqlfiddle.com/#!9/508ae6/27

select tmp1.User_ID,tmp1.User_No,User_Profile.User_Name,User_Profile.Nationality_Code , 
tmp1.Date_From,tmp1.Date_To 
from 
(
    select * from User_Transfer U 
    order by Date_From desc 
) as tmp1,User_Profile 
where 
tmp1.User_ID=User_Profile.User_ID 
group by User_ID 

Answer 4

尝试下面的查询

with temp as 
    (
    select t.user_id, 
    t.user_no, 
    p.user_name, 
    p.nationality_code, 
    max(Date_to) as Date_to 
    from user_transfer t inner join user_profile p 
    on t.user_id=p.user_id 
    group by t.user_id,t.user_no,p.user_name,p.nationality_code 
) 
select 
    a.user_id,a.user_no,p.user_name,p.nationality_code,a.date_from,p.date_to 
    from user_transfer a join temp p 
    on a.user_id=p.user_id 
    and a.date_to=p.date_to;