Question

I have a table which contains a timezone offset, +1, -7, +5 etc.
I have another, joinable, table which contains logging information including a datetime.

I would like to select out the datetime from the second table with the offset added on to it using for example, INTERVAL ‘1 hours’, INTERVAL ‘-7 hours’ etc.

My psuedocode would be something like:

SELECT l.status, l.inserted + INTERVAL (coalesce(timezone_offset, '0')||' hours' )  AS inserted FROM log l
LEFT OUTER JOIN users u on u.usersid = l.usersid
LEFT OUTER JOIN companies c on c.companiesid = u.companiesid 
WHERE l.usersid=?

This doesn’t work, but I can’t figure out how to make it work in PostgreSQL 8.3.

Any ideas?

Answer 1

It turns out you can multiply an INTERVAL by a number. So if I create an INTERVAL of ‘1 hours’ and multiply that by the stored offset, that will work, yielding:

SELECT l.status, l.inserted + (INTERVAL '1 hours' *  coalesce(timezone_offset, '0')) FROM log as l
LEFT OUTER JOIN users u on u.usersid = l.usersid
LEFT OUTER JOIN companies c on c.companiesid = u.companiesid 
WHERE l.usersid=?

et voila!