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#1 (**permalink**) 02-28-2008, 05:23 AM

What is the best way to UPDATE a row only if values are different? We
have a mainframe extract that literally has 100,000 rows and am worried
about the performance of just running INSERTs each night.

Is there a simple comparison command or would you have to nest a SELECT
statement? Thank you,

Nick

#2 (**permalink**) 02-28-2008, 05:23 AM

On 09/12/06, Nick Meyer <n.meyer@usa.net> wrote:
> What is the best way to UPDATE a row only if values are different? We
> have a mainframe extract that literally has 100,000 rows and am worried
> about the performance of just running INSERTs each night.
>
> Is there a simple comparison command or would you have to nest a SELECT
> statement? Thank you,
>
> Nick
>

You have to check the line first, then compare and update if
neseccary. I've been through that recently, and decided that it was
better to just UPDATE. Of course, I had much less rows than you do.

Maybe you could store an array of changed rows in whatever language
you are programming, then update from that? Or a text file, another
DB, whatever...

Dotan Cohen

http://what-is-what.com/what_is/digg.html
http://dramatherapy.info

#3 (**permalink**) 02-28-2008, 05:23 AM

Hello,
with good indeces 100 000 rows is basically nothing.

Give it a try.

Peter

Nick Meyer wrote:
> What is the best way to UPDATE a row only if values are different? We
> have a mainframe extract that literally has 100,000 rows and am worried
> about the performance of just running INSERTs each night.
>
> Is there a simple comparison command or would you have to nest a SELECT
> statement? Thank you,
>
> Nick
>
>

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only update if values different