"Martijn Tonies" <[EMAIL PROTECTED]> wrote on 09/07/2004 13:55:40:
> If you're de-normalizing
> your design to get better performance, then there's something
> wrong with the database engine (whatever engine that may be).
Nearly always, but not absolutely always. I have a table with columns
primary start
primary finish
secondary start
secondary finish
Since it is defined that the distance between start and finish is the same
for both primary and secondary, this is denormalised, since secondary
finish is always given by secondary start + (primary finish - primary
start). However, I want to use all four fields as indexes, including
secondary finish. Does any database allow indexes on complex functions of
columns rather than on columns themselves? Or is this just a defect in
MySQL?
Alec
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