Why is "ABCDEF" = "ABC" turning up TRUE in my code?

 The single equal sign operator (=) is not what you expect.
 If you have SET EXACT OFF (the default) then string comparisons
 only check as far as the length of the right-side value.
 If you want an exact match, then you should use the double-equals
 operator (==) instead.  Many programmers forget about it on
 purpose and just SET EXACT ON, but there are times (such as
 looking up a partial key) when the "fuzzy match" is useful.