Re: SQL Max question

Why do I prefer CTE's?

I like CTEs because I cannot split a (very) complex SQL statement into
smaller parts, but I can test each CTE on its own.
If you start nesting sub-selects, by no later than 3 nested sub-selects,
you cannot read the query anymore, ... and then try to test such a
sub-select.

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!"
„Train people well enough so they can leave, treat them well enough so
they don't want to.“ (Richard Branson)


-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of
Vernon Hamberg
Sent: Sonntag, 6. September 2020 15:18
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: SQL Max question

+1 on the OLAP solution - there is so much those functions can do for
us, the more clear examples, the better.

I also like the CTE more - it crossed my mind, not sure why I didn't
mention it, at least - maybe being in the middle of preparing for the
upcoming POWERUp Virtual Conference.

Why do I prefer CTE's? It's easier to see what is happening - nesting
adds some confusion, trying to separate THAT SELECT statement from the
one surrounding it, well, that can be a challenge.

Gotta love it! So many different ways to do things, right? One motto of
the PERL language contingent - TMTOWTDI - There's More Than One Way To
Do It!

Vern

On 9/6/2020 7:42 AM, Birgitta Hauser wrote:

You can do it with a nested sub-select, but I prefer a Common Table

Expression

With x as (Select #DID. Max(Status) MaxStatus
from YourTable
Group by #DID)
select a.*
from YourTable a join x on a.#DID = x.#DID;

You can also can get the result by using the ROW_NUMBER() OLAP

Specification:

With x as (Select a.*, Row_Number() Over(Partition by #DID Order By

Status Desc) RowNbr

from OrderDetx a)
Select *
from x
Where RowNbr = 1;

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!"

„Train people well enough so they can leave, treat them well enough so

they don't want to.“ (Richard Branson)

-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of

Vernon Hamberg

Sent: Sonntag, 6. September 2020 06:54
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx

Subject: Re: SQL Max question

Hello Art

If I may say back what I think you're saying -

You have a table with 1 row per DID# - that is, DID# is unique.

And status is not in this table.

And you want a result table that has all the columns from the first one,

plus a status column that has the highest status for the DID# in that row.

OK, I think you are getting close and can get this with a JOIN and a

nested table expression - you want the 2nd table to have the DID# and its
highest status in it - then JOIN to that.

select table1.*, table2max.maxstatus from table1
join (select did#, max(status) maxstatus from table2 group by did#)

table2max

on table1.did# = table2max.did#

Then you can do pretty much what you want - you could create a temp from

this using CREATE TABLE, for example, and make it based on this SELECT
statement.

HTH
Vern

On 9/5/2020 10:26 PM, Art Tostaine, Jr. wrote:

There is one row in my first table keyed by did. Other tables are
joined into this view but they are 1-1 by did. I joined it to a status
file that has Did and 1-20 statuses/rows.

In my new table I want all of the fields but only one row per did with
the highest status.

My goal is to create a temp table that I can run reports, extract to
csv, etc.

I wonder if I could create one row per did and then do an update with
a select from the status file getting only the max row from it.

On Sat, Sep 5, 2020 at 10:36 PM Alan Campin <alan0307d@xxxxxxxxx>

wrote:

I am not completely understanding what you are doing here but
normalizing

table structure?



Could you respond with what you see the table structure would look

like?

On Sat, Sep 5, 2020 at 6:52 PM Art Tostaine, Jr.
<atostaine@xxxxxxxxx>

wrote:

I have a table that has a DID#, many other columns, and a numeric
status field. I want the table to have all the columns and one row
per did#

with

the highest status value.
I'd like to either do a delete or create another temp table with
only

these

records. Is this possible?
I've looked at group by but that won't let me keep all columns in
the table.
I also checked out partition by but that's not what I want.
Thank you
--
Art Tostaine
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