AW: Fetch n rows from each group by.

Hi,

Window functions have been implemented in V5R4?

If you mean Row_Number(), Dense_Rank() and Dense(), Yes.
If you mean Recursive Queries (i.e. Recursive Common Table Expressions and
Recursive Views), Yes.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok)
"What is worse than training your staff and losing them?  Not training them
and keeping them!"

-----Ursprüngliche Nachricht-----
Von: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] Im Auftrag von Chris Payne
Gesendet: Wednesday, February 14, 2007 19:25
An: Midrange Systems Technical Discussion
Betreff: RE: Fetch n rows from each group by.


Window functions have been implemented in V5R4?

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of BirgittaHauser
Sent: Wednesday, February 14, 2007 2:03 AM
To: 'Midrange Systems Technical Discussion'
Subject: RE: Fetch n rows from each group by.

Hi,

I can provide a solution, if you are already on release V5R4. If you are not
yet on release V5R4, I'm not aware of an  easier way than writing and RPG
program with embedded SQL or an stored procedure or UDTF with SQL.

On release V5R4 you may try the following:
with x as (select  Row_Number() over(Partition By Region Order By Sales
Desc) RowNbr,
                   Region, Sales
              From Table
              Where ....) 
Select * from x
   Where RowNbr <= 5; 

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok) "What is
worse than training your staff and losing them?  Not training them and
keeping them!"

-----Ursprüngliche Nachricht-----
Von: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] Im Auftrag von Mike Pantzopoulos -
(H/O)
Gesendet: Wednesday, February 14, 2007 04:26
An: midrange-l@xxxxxxxxxxxx
Betreff: Fetch n rows from each group by.


I have used the FETCH n ROWS ONLY clause to return the first n records in a
select statement, but I now want to return the first n from each group, and
I'm damned if I can find any reference material for this. Can it be done?

 

In essence I want to return the top 5 agents from each region based on
sales. The following pseudo-SQL would show all the agents in reverse sales
order within region:

 

Select region, sales from file order by region, sales desc

 

If I want to select the first 5 in the entire return set I use:

 

Select region, sales from file order by region, sales desc fetch first 5
rows only

 

How do I write the SQL to return only the first 5 in each region without
having to use RPG?

 

TIA

 


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