Re: SQL - Slow Like or Between

I'm just throwing something out there... might not make a difference. But
let's try it. My wheels are spinning... :-)

Get a distinct count of each column in your where clause. Then order your
where clause so the field with the lowest distinct count first followed by
the second lowest and so on.


Another question, do any of these fields have a parent table? If you do,
I'm thinking that you can do this range/like selection on the smaller table
and use the IN clause with subselect from the parent table. i.e.

where field in (select field from parent_table where parent_value like
'SOME STRING%')
and field2 in (select field2 from another_parent where parent_value between
-999 and 999)

etc.

throwing something else out there to try... maybe... I say this because I
truly don't know, use your best judgement. If you don't have parent tables
on those fields... what happens if you create your own in qtemp. It will
obviously depend on how fast each of these create.

create table qtemp/table_field1 (
field1 char(10)
);

insert into qtemp/table_field1
select distinct field1
from table
where field1 between :field1_low and :field1_high;

repeat for the other columns. Again it depends on the speed of these.
If it's not fast then it's not worth it.

Using the qtemp tables.

select *
from invmstp
where (field1,field2,field3,field4,field5) in
(select field1, field2, field3, field4, field5
from qtemp/table_field1
, qtemp/table_field2
, qtemp/table_field3
, qtemp/table_field4
, qtemp/table_field5)

Remember to put the smallest distinct count columns first in the where
clause.


On Thu, Oct 24, 2013 at 1:52 PM, Michael Ryan <michaelrtr@xxxxxxxxx> wrote:

I will Steve, but I think I'll examine the code closer. I'm getting very
fast results in interactive SQL, and slow results in my service program
procedure/stored procedure/result set program. I'm going to look at some
work management issues too. Thanks!


On Thu, Oct 24, 2013 at 1:49 PM, Needles,Stephen J <
SNEEDLES@xxxxxxxxxxxxxxxx> wrote:

Ryan,

Can you post the SQL?

Steve Needles


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Michael Ryan
Sent: Thursday, October 24, 2013 11:59 AM
To: Midrange Systems Technical Discussion; RPG programming on the IBM i /
System i
Subject: SQL - Slow Like or Between

Note: Cross posted because it's SQL in RPG, but I think it's just an SQL
issue.

A continuation of an email that I sent a couple of days ago, and got some
good feedback. I'm returning a result set to RPG or PHP via a stored
procedure.

On further analysis, I need to provide a starting point for record

access.

I was using static SQL and a Between clause for each of 10 fields between
*LOVAL and *HIVAL. Takes too long to run...like 60 seconds over an 800K
record file.

I created individual indexes (EVI's) over each of the 10 possible

columns.

Tried static SQL with a technique like this: Where :xxvnda1 in (' ',
IMVNDA) And.... Still too slow.

Tried dynamic SQL by creating the statement using equal, like this:
SQLStmt = SQLStmt + cBlank + 'IMVNDA =' + cBlank + cQuote + xxvnda1 +
cQuote; Much faster when looking for an equal, but doesn't return records
that don't match exactly.

Tried dynamic SQL using Like, and it's as slow as the initial static
technique.

I'm going to try dynamic SQL using a Between clause, but not as far as
*LOVAL and *HIVAL, and only including the columns I want to search in the
Where clause. I'm not anticipating good results though.

Question (finally): What's the best technique for an SQL-based search
where I return a result set from a search of multiple fields?

Thanks for any ideas.
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