[AccessD] xyz* faster than *asd

And making a fast answer is not the wise...

The last line of my answer should be:
So having an index on the search field will allways make a LIKE xyz*
query by far faster than a LIKE *xyz query.

Asger

----- Original meddelelse -----

> Fra: Asger Blond <ab-mi at post3.tele.dk>
> Til: Access Developers discussion and problem solving
> <accessd at databaseadvisors.com>
> Dato: Lør, 09. jul 2011 00:19
> Emne: Re: [AccessD] xyz* faster than *asd
> 
> Too bad you got this silly answer in your way back SQL class. Because
> it's quite obvious why a LIKE xyz* will be faster than LIKE *xyz on
> an
> indexed field. For a LIKE *xyz the query engine have to investigate
> each
> and every record, because it just doesn't know what leading
> characters to
> seach - and this traversing all records is what's called a "table
> scan".
> For LIKE xyz* the query engine can use the index, because it know
> that
> the leading characters are "xyz". So having an index on the search
> field
> will allways make a LIKE *xyz query by far faster than a LIKE xyz*
> query.
> Asger
> 
> ----- Original meddelelse -----
> 
> > Fra: John Bartow <john at winhaven.net>
> > Til: 'Access Developers discussion and problem solving'
> > <accessd at databaseadvisors.com>
> > Dato: Fre, 08. jul 2011 23:38
> > Emne: Re: [AccessD] xyz* faster than *asd
> >
> > I remember asking a similar question in an SQL queries class about
> 20
> > years
> > ago. I believe the answer was "because".
> >
> > Its Friday ;o)
> > -----Original Message-----
> > From: accessd-bounces at databaseadvisors.com
> > [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of jwcolby
> > Sent: Friday, July 08, 2011 12:25 PM
> > To: Access Developers discussion and problem solving
> > Subject: [AccessD] xyz* faster than *asd
> >
> > Does anyone know of a reason that LIKE is faster with the * in back
> > instead
> > of the front of a string to search by in the where clause?
> >
> > --
> > John W. Colby
> > www.ColbyConsulting.com
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> >
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> 
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