VB Forum / Database Access / January 2007

Hopefully someone that truly 'knows' will come in here and make it clearer.
But the explanation that I have always been given is because the Like
Statement does a simple text comparison, skips the 'optimizer', and thus
allows a quick bail (short-circuit). Just marches down the file pulling
whatever "fits".

However, this phenomena is confined mostly to ISAM databases or those with
ISAM roots or binary text compare'ers (eg, Jet). And of course depends on
the data type. In dbf files everything is ASCII (text).

hth
-ralph

Hi Darrell,

I haven't tested but you may be interested in what the VFP Help says about
the ANSI setting for SQL queries. You can change the ANSI setting by issuing
SET ANSI ON or OFF.

     Visual FoxPro 9.0 Language Reference
     SET ANSI Command

     In the Visual FoxPro OLE DB Provider, you cannot query the value of
ANSI using the SET command though SET ANSI is supported.

SET ANSI ON | OFF

Specifies whether to pad a shorter string with spaces when making a SQL
string comparison or binary expression with zero (0) bytes when making a
binary expression comparison in SQL commands using the equal sign operator
(=).

     Note
     In the Visual FoxPro OLE DB Provider, you cannot query the value of
ANSI using the SET command though SET ANSI is supported.

SET ANSI ON | OFF

Parameters
 ON
 Pads the shorter string or binary expression with spaces or zero (0) bytes
needed, respectively, to make it equal to the length of the longer string or
expression. When SET ANSI is set to ON, the two strings or expressions are
compared character for character for their entire lengths.

 OFF
 Specifies that the shorter string not be padded with spaces or binary
expression not be padded with zero (0) bytes. (Default)

 When SET ANSI is set to OFF, the two strings are compared character for
character until the end of the shorter string is reached.

Remarks
SET ANSI has no effect on the double equal sign (==) operator. When you use
the == operator, the shorter string or binary expression is always padded
with spaces or zero (0) bytes, respectively, for the comparison. For more
information, see Relational Operators.

.......

String Order   In SQL commands, the left-to-right order of the two strings
in a comparison is irrelevant - switching a string from one side of the = or
== operator to the other doesn't affect the result of the comparison.
<<

Also, you should know that the FoxPro Rushmore technology will speed up
queries when the expression in the Where or Join clauses exactly matches the
expression in an index on the table.