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Undocumented feature of Indexing
Message
 
 
To
09/03/2000 00:30:14
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Miscellaneous
Thread ID:
00343211
Message ID:
00343605
Views:
20
>All in all, it doesn't really work! :) The real problem (bug, IMHO) is that VFP accepts indexes on variable length
>char expressions. And regardless of any advice you may get from anybody in favor of such indexes, I can't advice
>against enough. The problems generated by such indexes are subtle and, usually, hard to find and hard to fix.
>
>Vlad

Hi Vlad,
In going through the thread yesterday, it turns out VFP doesn't really allow variable length key expressions. It derives the key length from the current record.

So if the record pointer was on a record with a memo field value greater than 240 characters in length, it bombed. The same can be said if the current memo field was empty. But, if the length falls within the valid range then the index is created with the key length matching that record.

As Ed pointed out, this can throw your sorting off if you have values greater in length than the generated key with similar starting characters.
Larry Miller
MCSD
LWMiller3@verizon.net

Accumulate learning by study, understand what you learn by questioning. -- Mingjiao
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