Re: SELECT and DATE Function question - Mailing list pgsql-admin

From Tom Lane
Subject Re: SELECT and DATE Function question
Date
Msg-id 22488.1157983704@sss.pgh.pa.us
Whole thread Raw
In response to Re: SELECT and DATE Function question  ("Aaron Bono" <postgresql@aranya.com>)
Responses Re: SELECT and DATE Function question  ("Aaron Bono" <postgresql@aranya.com>)
List pgsql-admin
"Aaron Bono" <postgresql@aranya.com> writes:
> Use:

> select start_date + (cast(number_of_days as text) || ' days')::interval from
> blah

This is a pretty awful way to do it, much better is

    select start_date + number_of_days * '1 day'::interval ...

which reduces to basically one multiplication instead of conversion to
text, text string append, parse interval string value (relying on a
couple of undocumented cast abilities).

But the real question here is whether you actually want sub-day
precision in your result.  Should the column have been 'date' rather
than 'timestamp' to begin with?  If not, what behavior are you expecting
at DST boundaries?

            regards, tom lane

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