>I have just learned, much to my chagrin, about SET ANSI ON. Having learned about its existence, I want to make sure I get it right ...
>
>It appears that when using '=' within a SELECT statement and SET ANSI OFF, the trailing spaces are ignored, and the comparison is only made up to the length of the shortest string. This "KP3 " = "KP31 ", even though normal VFP string comparison doesn't work this way.

The trailing blanks are not ignored whith SET ANSI OFF so "KP3 " will not equal to "KP31 "
The string comparison is controlled by SET EXACT. By default it set to OFF in which case comparison is performed to the length of the string on the right.


>However, setting SET ANSI ON will compare the strings to their entire lengths, so such mis-matches do not occur. Is this correct? Is there any other effect of SET ANSI ON?

Almost. The shorter string will be padded with spaces to the lenght of the longer one before comparison.