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Help with Over Partition  in a CTE

Posted on 2013-11-08
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Last Modified: 2013-11-08
Below is a simplified CTE and the result set.

With MstrTable(IDNo, RelNo)
as (Select IDNo, RelNo From TableA where xxx
Union
Select IDNo,RelNo from TableA where yyyy)
Select IDNo,RelNo From MstrTable Order by IDNo, RelNo

Results
IDNo          RelNo
1                   1
2                   1
3                   1
3                   2
4                   1

Desired result Set
IDNo          RelNo
1                   1
2                   1
3                   2
4                   1

I want the result set to contain only one entry for the IDNo and the MAX RelNo (see IDNo = 3 above).
With a single query in the CTE, without the UNION, Over Partition works great. But I do not think that will work as anticipated with the UNION. How do I get the result set to display a single value for IDNo and the Maximum value for RelNo?
Thanks,
pat
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Question by:mpdillon
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LVL 32

Expert Comment

by:awking00
ID: 39633511
Without any understanding of what the where clauses are doing, it's hard to see why you would even need a union with both select statements querying the same table. However, given that it's necessary, would the MAX RelNO come from the first or second select statement or from either? I see no reason why an analytical query can't be used with a common table expression. Perhaps you can provide some sample data, with a little more explanation of the where clauses, and your expected results.
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Author Comment

by:mpdillon
ID: 39634230
Thanks.
I have attached a file which contains create table statements plus populates the tables with data.

The Raw data is:

IDNo   RelNo   LastModDt
 1             1        '10/01/2013'
 1             2        '11/01/2013'
 2             1        '10/07/2013'
3              2        '11/06/2013'
4              1        '11/04/2013'
3              1        '10/21/2013'
2              2        '10/22/2013'

Desired Result
 1             2        '11/01/2013'
 2             2        '10/22/2013'
 3             2        '11/06/2013'
 4             1        '11/04/2013'

My initial CTE looks like:

with mstrTable (IDNo, RelNo, LastModDt)
as
(
Select IDNo, relNo, LastModDt from TableA
union
Select IDNo, Relno, LastModDt from TableB
)
Select IDNo, RelNo, LastModDt from mstrTable

But I cannot figure out how to get the result set down to the Desired result above.

Thanks,
pat
frmProducitonLookup-query.txt
0
 
LVL 32

Expert Comment

by:awking00
ID: 39634344
with mstrTable (IDNo, RelNo, LastModDt)
as
(
Select IDNo, relNo, LastModDt from TableA
union
Select IDNo, Relno, LastModDt from TableB
)
Select IDNo, RelNo, LastModDt from
(Select IDNo, RelNo, LastModDt,
 row_number() over (partition by IDNo order by LastModDt desc) rn
 from mstrTable) as x
where x.rn = 1;
0
 
LVL 32

Accepted Solution

by:
awking00 earned 500 total points
ID: 39634345
with mstrTable (IDNo, RelNo, LastModDt)
as
(
Select IDNo, relNo, LastModDt from TableA
union
Select IDNo, Relno, LastModDt from TableB
)
Select IDNo, RelNo, LastModDt from
(Select IDNo, RelNo, LastModDt,
 row_number() over (partition by IDNo order by LastModDt desc) rn
 from mstrTable) as x
where x.rn = 1;
0
 

Author Closing Comment

by:mpdillon
ID: 39634440
That was it. Thank you. I replaced the LastModDt in the Partition with RelNo otherwise it worked perfectly.
thanks.
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