RE: Using an SQL index over DDS file?

I usually agree with your SQL advice, Charles, but in this case my
experience differs.

SELECT PRSTAT, PRTYPE FROM PRPMS GROUP BY PRSTAT, PRTYPE ;
SELECT COUNT(*) FROM PRPMS ;

The first statement will return 37 rows on this system, none of which are
duplicates.
The second returns a value of 11,321.

The way I read your reply, I should expect 11,321 rows returned in the first
query.

Dennis Lovelady
http://www.linkedin.com/in/dennislovelady
--
?...Yes, the lectures are optional. Graduation is also optional.?
-- Professor Brian Quinn

Actually no it won't.

Select distinct fld1, fl2
from file

would give one row in the results set for every combination of fld1,
fld2

Select fld1, fl2
from file
group by fld1, fld2

would give you as many rows as the original table, with duplicates for
the rows with the same fld1, fld2.

In order for a solution using GROUP BY to work, you also need an
aggregate function of some sort...
Select fld1, fl2, count(*) as theCount
from file
group by fld1, fld2

HTH,
Charles

On Mon, Jul 26, 2010 at 2:33 PM, Schutte, Michael D
<Michael_Schutte@xxxxxxxxxxxx> wrote:

One suggestion...

Do a select  group by query versus a select distinct.

Select  fld1, fld2

From file

Group by fld1, fld2

Would give the same requests as

Select distinct fld1, fld2

Just try to see if VE gives a different answer.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-

bounces@xxxxxxxxxxxx] On Behalf Of Loyd Goodbar

Sent: Monday, July 26, 2010 2:25 PM
To: Midrange Systems Technical Discussion
Subject: Re: Using an SQL index over DDS file?

Thanks for the replies.

Luis, index advisor does not recommend any indexes. If I put a

qualifier in

the select, such as "where i1azcd='WV'", VE shows the index in use

but the

run time is the same, between 60 and 90 seconds. I was hoping that

since I

select only the columns from the index it would perform much faster.

As to

any gotchas, I was referring akin to runtime performance: will the

query

perform differently because I call it from iNav or STRSQL or embedded?

Michael, I try to create new database objects with SQL. As you

suggested, I

created a logical file. However, even selecting directly against the

LF, VE

reports a table scan is performed.

Charles, there are 14 indexes on the table, including this one.

Running the

query with STRDBG and STRSQL did not yield any messages or index

advice. VE

reported the query optimizer did not time out. It reports "Indexes

exist but

none could be used".


I can't do more testing until I reboot, as Run SQL Scripts now

refuses to

run scripts or VE.

Thanks again,
Loyd
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