问题
Afternoon/Evening all,
I'm looking for the final touches to the below query. I need to remove the duplicate occurrences of a column in a particular row. Currently using the below SQL:
SELECT CBNEW.*
FROM CallbackNewID CBNEW
INNER JOIN (SELECT IDNEW, MAX(CallbackDate) AS MaxDate
FROM CallbackNewID
GROUP BY IDNEW) AS groupedCBNEW
ON (CBNEW.CallbackDate = groupedCBNEW.MaxDate) AND (CBNEW.IDNEW = groupedCBNEW.IDNEW);
My result set looks like the below
ID RecID Comp Rem Date_ IDNEW IDOLD CB? CallbackDate
138618 83209 1 0 2012-03-16 12:40:00 83209 83209 2 16-Mar-12
138619 83209 1 0 2012-03-16 12:40:00 83209 83209 2 16-Mar-12
110470 83799 1 0 2011-07-27 11:46:00 83799 83799 10 27-Jul-11
110471 83799 1 0 2011-07-27 11:46:00 83799 83799 10 27-Jul-11
This however gives me duplicate values in the CallBackDate and IDNEW Column because in the table there are some different Primary Keys with the same IDNEW and CallbackDate values.
If I dump this result into Excel, I can just use remove duplicates on the first ID column, and the problem's solved.
But what I want to do is make sure my result only includes the FIRST instance of the ID column, where IDNEW and CallbackDate are duplicated.
I'm sure I just need to append a tiny piece of SQL, but I'm stuck if I can find the answer so far.
Your help is very much appreciated.
回答1:
Try adding MIN(ID)
to the inner query and then adding it also on the ON
clause:
SELECT CBNEW.*
FROM CallbackNewID CBNEW
INNER JOIN (SELECT IDNEW, MIN(ID) AS MinId, MAX(CallbackDate) AS MaxDate
FROM CallbackNewID
GROUP BY IDNEW) AS groupedCBNEW
ON (CBNEW.CallbackDate = groupedCBNEW.MaxDate)
AND (CBNEW.IDNEW = groupedCBNEW.IDNEW)
AND (CBNEW.ID = groupedCBNEW.MinId) ;
sqlfiddle demo
回答2:
Here is a rather "brute force" approach. It just takes the results of your original query and does Min()
on [ID], Max()
on [Comp] and [Rem], and GROUP BY
on everything else:
SELECT
Min(t.ID) AS MinOfID,
t.RecID,
Max(t.Comp) AS MaxOfComp,
Max(t.Rem) AS MaxOfRem,
t.Date_,
t.IDNEW,
t.IDOLD,
t.[CB?],
t.CallbackDate
FROM
(
SELECT CBNEW.*
FROM
CallbackNewID CBNEW
INNER JOIN
(
SELECT IDNEW, MAX(CallbackDate) AS MaxDate
FROM CallbackNewID
GROUP BY IDNEW
) AS groupedCBNEW
ON (CBNEW.CallbackDate = groupedCBNEW.MaxDate)
AND (CBNEW.IDNEW = groupedCBNEW.IDNEW)
) t
GROUP BY
t.RecID,
t.Date_,
t.IDNEW,
t.IDOLD,
t.[CB?],
t.CallbackDate;
It might not be terribly elegant, but if it works....
回答3:
In MS SQL Server, I think you are looking for the ROW_NUMBER()
function.
Something like this should help you get what you are looking for:
SELECT
X.*
FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY DBNEW.IDNEW, DBNEW.MaxDate) [row_num]
FROM
CallbackNewID CBNEW
INNER JOIN
(
SELECT
IDNEW,
MAX(CallbackDate) AS MaxDate
FROM
CallbackNewID
GROUP BY
IDNEW
) AS groupedCBNEW ON (CBNEW.CallbackDate = groupedCBNEW.MaxDate) AND (CBNEW.IDNEW = groupedCBNEW.IDNEW)
) X
WHERE
X.row_num = 1
回答4:
SELECT
A.*
FROM
(SELECT
*,
ROW_NUMBER() OVER (PARTITION BY IDNEW ORDER BY CallbackDate DESC)
AS [row_num]
FROM CallbackNewID
) A
WHERE
A.row_num = 1
来源:https://stackoverflow.com/questions/19774273/remove-duplicates-in-sql-result-set-of-one-table