[dba-SQLServer] Covering Indexes

Hi John,

It depends...

I've used covering indexes occasionally but only where all participants
are used say >50% of the time. 

IIRC the covering index was used only when each field is actually used.
I think the column order was important too!

What I do do is check the execution plan for every Select statement I
run on SQL when I create it.
I try and get 100% seek action happening, either CI Seek or Seek.
In your case with your db from hell I suspect your are just going to
have to test to see what works best for each situation.

Good luck

Michael M

Subject: [dba-SQLServer] Covering Indexes

I need to understand covering indexes.  One of my databases has fields
such as 

PresenceOfChildren_00_02
PresenceOfChildren_03_05
PresenceOfChildren_06_10

Etc.  Thus what I need to know is do I need an individual index on each
field?  I get requests for data using selection criteria on just one,
and also sometimes on more than one of these fields.  If I have an index
on all of these fields together, will that help a query with selection
criteria for a single one of these fields?  On 3 out of 7 of these
fields etc?

John W. Colby
Colby Consulting
www.ColbyConsulting.com 

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