Speed Difference

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#693

From: Jason Summers
Date: Sat, 03 Nov 2007 01:38

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Hello Again,

I'm curious as to the speed of the UNION statement.  I have a CONTACTS 
table, which contains phone number prefix fields: HPHONEPREFIX, 
MPHONEPREFIX, (and others, but we'll omit those for brevity).  These fields 
are indexed.

Comparing these two statements:  Say I want all people who have any phone 
number with '573' prefix.

select CONTACTID from CONTACTS where (HPHONEPREFIX = '573') OR (MPHONEPREFIX 
= '573')

As compared to this:
select CONTACTID from CONTACTS where HPHONEPREFIX = '573'
UNION
select CONTACTID from CONTACTS where MPHONEPREFIX = '573'

Will there be extra overhead using UNION?

Thanks,
- Jason

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Subject: Speed Difference
Date: Fri, 2 Nov 2007 20:38:04 -0500
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