Re: day interval - Mailing list pgsql-general

Date subtraction returns the integer data type; timestamp subtraction returns the interval datatype.

postgres@haggis:~$ psql test
psql (9.6.15)
Type "help" for help.

test=# select date('20191001') - date('20190923');
 ?column?
----------
        8
(1 row)

test=# select date('2019-10-01') - date('2019-09-23');
 ?column?
----------
        8
(1 row)

test=# select cast('2019-10-01 00:00:00.000' as timestamp) - cast('2019-09-23 00:00:00.000' as timestamp);
 ?column?
----------
 8 days
(1 row)

test=# select pg_typeof(cast('2019-10-01 00:00:00.000' as timestamp) - cast('2019-09-23 00:00:00.000' as timestamp));
 pg_typeof
-----------
 interval
(1 row)

Thanks Andrew.

My code fails since the expression (In a PG/PG SQL function) which assumes integer result
Now produces the string '8 day';

This has been working for years on all PG community servers.

This happens on an EDB PG 9.6.3.

I know the fix, but I need the ability to create the bug in my server, and I do not know how.

Thanks

Danny


-----Original Message-----
From: Andrew Gierth <andrew@tao11.riddles.org.uk> 
Sent: Saturday, October 12, 2019 6:26 PM
To: Abraham, Danny <danny_abraham@bmc.com>
Cc: pgsql-general@postgresql.org
Subject: [EXTERNAL] Re: day interval

"Abraham" == Abraham, Danny <danny_abraham@bmc.com> writes:

Abraham> HiAbraham> A question on day interval
Abraham> select date('20191001') - date('20190923');
Abraham> Will provide sometimes '8' - an integer , but sometimes '8  Abraham> day' - a string

No, it'll always return an integer. You will only get an interval result if you subtract timestamps rather than dates, for example if one of the operands is actually an expression returning a timestamp.

Give an example of an actual expression you used that returned an interval instead, and we may be able to tell you how to fix it.

--
Andrew (irc:RhodiumToad)