Re: Embedded SQL/Complex Statement/Speed

[Luis Rodriguez <luisro58@xxxxxxxxx>]

Michael,

Go to iNav, SQL Scripts. Write a prototype of your statement, just the
SELECT part, and run it with VE (only the explain part). VE's advisor would
show you (if needed) a recommendation for any required indexes.

HTH,

Luis Rodriguez
IBM Certified Systems Expert — eServer i5 iSeries
--



On Wed, Mar 23, 2011 at 3:46 PM, Michael Ryan <michaelrtr@xxxxxxxxx> wrote:

> Well, here's another. I have an SQL statement that looks like this:
>
> C/Exec SQL
> C+ DECLARE C1 CURSOR FOR
> C+    Select * From MYFILE
> C+    Where Imfld1 Between :HostFld1  and :HostFld2
> C+          And Imfld2  Between :HostFld3  and :HostFld4
> C+          And Imfld3  Between :HostFld15 and :HostFld16
> C+          And Imfld4  Between :HostFld17 and :HostFld18
> C+ Order By Case When :DspSort = 1 Then Imfld1 Else NULL End,
> C+          Case When :DspSort = 1 Then Imfld2  Else NULL End
> C+ For Read Only
> C/End-Exec
>
> This is a simple example - some are more complex (as in more
> comparisons). Using the Between clause is great with high and low
> values, but it can be very slow. How do I attack a problem like this?
> How do I know what indexes or views or whatever to make? Do I even
> want to do that? I know this is incomplete information, but I have to
> start somewhere.
>
> Cross posted since it's RPG but it's SQL in nature.
>
> Thanks!
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