Max width for indexed column?

Is column width a factor for an indexed column? Would indexing a
VARCHAR(100) be a bad idea? Any links to discussion of this topic?
Thanks for your advice.
- Joe Geretz -'bad' is of course a relative term...
Yes, width of an index will affect performance. This is a LONG topic, but
here a a few thoughts...
* width of a clustered index can be more important to worry about than a NC
index since a clustered index key is propogated through ALL the NC indexex.
* yes, width does matter. Intuitively, it just makes sense. There is less
CPU and much less IO involved for a 10 byte index than a 100 byte index.
Would it be quicker for you to read a list of 10 letter words or 100 letter
sentences? Of course that's a silly example, but yes... narrow indexes will
be better all things considered.
* having a wide index isn't the end of hte world and probably isn't a big
deal with smaller data sets.
* if you DO need to index wide char based fields and you are worred about
performance... you may want to consider creating a checksum based on the
chat column and indexing the checsum col (which will be an integer). That
would be much faster...
Brian Moran
Principal Mentor
Solid Quality Learning
SQL Server MVP
http://www.solidqualitylearning.com
"Joseph Geretz" <jgeretz@.nospam.com> wrote in message
news:e7LEw0RiEHA.344@.TK2MSFTNGP10.phx.gbl...
> Is column width a factor for an indexed column? Would indexing a
> VARCHAR(100) be a bad idea? Any links to discussion of this topic?
> Thanks for your advice.
> - Joe Geretz -
>