RE: Omit record from SQL AVG based on field value

["Elvis Budimlic" <ebudimlic@xxxxxxxxxxxxxxxxxxxxxxxxx>]

NULL means "void of value" so it cannot be manipulated with any arithmetic
operations, including SUM & AVG.  Think of it as being "skipped", which is
what you're after in this case.

Take a look at that example.

There are number of problems with your statement.... like GROUP BY a single
field when you're projecting multiple fields - that won't work.

You're better of starting from scratch with your SQL statement.  Forget
GROUP BY.  AVG all rows, making sure fields without value are cast to NULL
using CASE clause.

Elvis

Celebrating 10-Years of SQL Performance Excellence

-----Original Message-----
Subject: RE: Omit record from SQL AVG based on field value


Elvis,

I thought about using case to replace bad values with null but that will
still include the record in the count won't it?  Or, does it keep a
separate count of occurrences by field?  Maybe I'm making this harder
than it is.

Rick

> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx
> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Elvis Budimlic
> Sent: Friday, February 02, 2007 1:35 PM
> To: 'Midrange Systems Technical Discussion'
> Subject: RE: Omit record from SQL AVG based on field value
>
> Rick, I don't know where to start with your SQL statement,
> it's too much work for Friday afternoon :(
>
> I do believe that what you need is to simply ignore the
> fields where you have no values by casting them to NULLs. 
> You do this with CASE clause.
> I googled and found this link that illustrates the point:
>
> http://www.craigsmullins.com/ssu_0899.htm
>
> See SQL statement #3.
>
> If you can simplify your statement or at least narrow down
> the problem, post back.
>
> Elvis
>
> Celebrating 10-Years of SQL Performance Excellence

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