At 01:30 PM 21-01-02 +0200, you wrote:

>> >>It is a Very Bad Idea to involve dates in keys, too.
>>>not my idea.
>>>The world out there requires that.
>
>> No, the world out there doesn't require you to involve dates in keys. The
>world out there requires movement numbers to be unique within year.
>
>For ex, is there a faster way than using a date index for finding the number
>of patients and number of tests that are being studied for every month in
>the year before? Should I get the rec.no of the first and get the rec.no
>of the last patient for an interval first and use rec.no as an index instead
>of a Datetime field? I tried that, but using a numeric index didn't increase
>the performance that I could notice.

It sounds OK to me. Dates are double precision numerics so they are good for indexing searches and for some kinds of sorts. But, because of the likelihood of mismatches arising from precision errors, they are not good as keys, or for exact-match searches.

--hb


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