Morgan,
> I am writing an app that will need to do some calcs based on
> differences
> between when a record is first inserted and when it is last updated.
> I have seen a lot of column::data-type in this list but can't find
> the
> relevant section in the documentation. Can anyone point me in the
> right
> direction?
Hmmm... apparently the docs on date/time data types could use some work.
Or some highlighting. Or something. We get this question every week.
I'll do it -- can I submit a FAQ in plain text?
Anyway, Morgan, thanks to Postgres' robust and ANSI-compliant support of
operators, computing intervals is quite simple. DATETIME is a "pure"
time value; DATE is an integer representation of time, with days as
whole numbers.
Thus:
DATETIME - DATETIME = INTERVAL
DATE - DATE = INTEGER
I don't know what's easier for you to work with; DATE/INTEGER is easier
for math, and DATETIME/INTERVAL is easier for calendar comparisons.
See the docs on data types, functions, and operators at PostgreSQL.org.
-Josh Berkus
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