From: | Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> |
---|---|
To: | Itai Zukerman <zukerman(at)math-hat(dot)com> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Time Aggregates |
Date: | 2000-08-02 15:27:13 |
Message-ID: | 39883DD1.610A0954@alumni.caltech.edu |
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Thread: | |
Lists: | pgsql-sql |
> I'm currently doing this:
> SELECT symbol, date_trunc('minute', posted),
> min(price), max(price), avg(price)
> FROM trade
> GROUP BY symbol, date_trunc('minute', posted);
> to get a list of minute-averages of trade prices. I get the feeling
> that this is bad form, that I should be doing this some other way. Is
> that the case?
Looks OK to me. If you are doing this *a lot* (i.e. many more queries
than inserts), then you might want to set up another column which
contains date_trunc('minute',posted) to avoid the calculation. Something
like
create table trade (
symbol text,
posted timestamp,
price integer,
mpost timestamp
)
then define a rule to update mpost when posted gets set (haven't done
that part).
- Thomas
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