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  3. September 2004

RE: fast search or scan for words in selected field

You're right - the LIKE predicate has to look through the entire field if it has the wildcard at the beginning.

The suggestion to use SOUNDEX to reduce disk space usage sounds (heh) good to me. There'd be a max length of 4, and SQL has a SOUNDEX() function. The words in "MY TEST COMPANY" would have the following soundex values:

MY    TEST  COMPANY
M000  T230   C515

There's not much point in the shorter words, since ME and MA and MI and MY would all get the value M000. And case is ignored.

Searches could still use

WHERE indexval = soundex(:search)

or

WHERE soundex(:search) = indexval

BTW, indexes might not be used because of the derived expression, according to the Indexing Strategies paper from IBM.

Vern

At 12:31 PM 9/10/2004, you wrote: 
I'm with Joe on this one.  I can't see how indices would help with
substring searches.  Then again, just because I can't comprehend it
doesn't mean it wouldn't.

Rob Berendt
--
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com

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