I have a table with the following structure (dummy column names and data):
+--+--+--+--+------+--------+
|a |b |c |d |issue |content |
+--+--+--+--+------+--------+
|a |b |c |d |1 | |
|a |b |c |d |2 | |
|a |b |c |d |3 | |
|d |e |f |g |1 | |
|d |e |f |g |2 | |
|e |f |g |h |1 | |
+--+--+--+--+------+--------+
My primary key contains columns a, b, c, d and issue.
I need a statement that first filters / groups by columns a, b, c and d and then only selects the record with MAX(issue). For this example the result set should look like this:
+--+--+--+--+------+--------+
|a |b |c |d |issue |content |
+--+--+--+--+------+--------+
|a |b |c |d |3 | |
|d |e |f |g |2 | |
|e |f |g |h |1 | |
+--+--+--+--+------+--------+
I know how I would do this for one specific record, but I cannot figure out how to do it for all the records:
SELECT TOP 1 * FROM Test_Max_N_Per_Group
WHERE a = 'a' AND b = 'b' AND c = 'c' AND d = 'd'
ORDER BY issue DESC
I am using Microsoft SQL Server 2008 R2.
// Edit: Thank you guys, I found this (very compact) solution in another topic :
SELECT t1.* FROM Test_Max_N_Per_Group t1
LEFT JOIN Test_Max_N_Per_Group t2
ON t1.a = t2.a AND t1.b = t2.b AND t1.c = t2.c AND t1.d = t2.d AND
t1.issue < t2.issue
WHERE t2.issue IS NULL
Try this:
;with cte as
(select a,b,c,d, issue, row_number() over (partition by a,b,c,d order by issue desc) maxval, content
from yourtable)
select a,b,c,d,issue,content
from cte
where maxval = 1
That row_number() does your ranking for you over groups defined by unique combinations of a,b,c and d.
Isn't this just a plain group by?
SELECT a, b, c, d, MAX(issue)
FROM tablename
GROUP BY a, b, c, d
If contents also is required:
SELECT a, b, c, d, issue, contents
FROM tablename t1
WHERE issue = (select max(issue) from tablename t2
where t1.a = t2.a
and t1.b = t2.b
and t1.c = t2.c
and t1.d = t2.d)
Will list both rows if it's a tie!
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