date_arithmetic revisited

Herouth,

I am doing this:

psql tracker -qtc "select date_part('epoch', '$edate'::datetime);" > .arg1
psql tracker -qtc "select date_part('epoch', '$sdate'::datetime);" > .arg2
date1=`cat .arg1`;
date2=`cat .arg2`;
psql tracker -qtc "select ($date1 - $date2) / 60 / 60 / 24;"

to calculate intervals...this is census stuff.
How many Pt Days per bed, etc.

Is there a way/function that allows me to do simple date arithmetic,
ala, `SELECT $enddate - startdate;' ?

Cheers and thanks,
Tom

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Thomas Good MIS Coordinator
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