如何使用聚合列獲取非聚合列的值？

Question

我有這樣的樣表：

ColA ColB ColC 
CBCP 25 popx 
ABC1 10 ppp1 
ABC1 25 ppxx 
CBCP 30 xm2x 

從那裏我想獲得這些列

ColA ColB ColC 
ABC1 25 ppxx 
CBCP 30 xm2x 

我希望的是獲得與最大COLB行。但我得到的錯誤，當我嘗試包括COLC我的查詢：

select ColA, max(ColB), ColC 
from tblCaseDev 
where ColB > getdate() group by ColA 

這是我的錯誤..

Msg 8120, Level 16, State 1, Line 1 
Column 'tblCaseDev.ColC' is invalid in the 
select list because it is not contained in either 
an aggregate function or the GROUP BY clause. 

希望有人可以幫助我..在此先感謝..

Answer 1

SELECT 
CaseNo,Date,Remarks, 

(SELECT max(cast(Date as datetime)) FROM tblCaseDev subc WHERE subc.CaseNo=c.CaseNo Group by c.CaseNo) AS MaxEntryDate 

FROM tblCaseDev c 

order by CaseNo 

Answer 2

您可以用遞減其ROW_NUMBER()每個組ColA並下令生成序列號通過ColB。

SELECT  ColA, ColB, ColC 
FROM 
      (
       SELECT ColA, ColB, ColC, 
         ROW_NUMBER() OVER(PARTITION BY ColA 
              ORDER BY ColB DESC) rn 
       FROM tablename 
     ) x 
WHERE  rn = 1 

• SQLFiddle Demo

如果你想獲得這ColB佔用了多條記錄，則可能需要將其更改爲DENSE_RANK()。

• TSQL Ranking Functions

Answer 3

您想使用的row_number()窗函數：

select CaseNo, "Date", Remarks 
from (select t.*, row_number() over (partition by caseno order by date desc) as seqnum 
     from tblCaseDev t 
     where date > getdate() 
    ) t 
where seqnum = 1; 

編輯：

你可以這樣做的老式方法，如果你沒有做row_number() ：

select t.* 
from tblCaseDev t join 
    (select caseno, max(date) as maxdate 
     from tblCaseDev 
     group by caseno 
    ) tsum 
    on t.caseno = tsum.caseno and t.date = tsum.maxdate 

Answer 4

您可以先創建一個聚合查詢，然後將原始表連接到聚合查詢。

例子：

SELECT 
    A.CaseNo, 
    A.Date, 
    B.Remarks 
FROM (
    SELECT 
     CaseNo, 
     MAX(Date) 
    FROM tblCaseDev 
    WHERE Date > GetDate() 
    GROUP BY CaseNo 
) A 
JOIN tblCaseDev B 
    ON A.CaseNo = B.CaseNo 
    AND A.Date = B.Date