I am trying to retrieve time difference in minutes from a table(login_history as t1) using postgresql .
When i tried this code
((date_part('hour', timestamp '2014-04-25 09:44:21')- date_part('hour', timestamp '2014-04-25 08:32:21'))*60 +(date_part('minutes', timestamp '2014-04-25 09:44:21')- date_part('minutes', timestamp '2014-04-25 08:32:21'))) as TimeNew
It works fine. But when i tried to retrieve information from a table t1 using this code
((date_part('hour', timestamp t1.login_date)- date_part('hour', timestamp t1.logout_date))*60 +
(date_part('minutes', timestamp t1.login_date)- date_part('minutes', timestamp t1.logout_date))
) as TimeNew
It throws this error
SQLSTATE[42601]: Syntax error: 7 ERROR: syntax error at or near "t1"
Thanks
I would use the interval that results from subtracting two timestamps for a much simpler expression:
select extract (epoch from (timestamp '2014-04-25 09:44:21' - timestamp '2014-04-25 08:32:21'))::integer/60
(gives 72)
or for your table:
select extract (epoch from (t1.logout_date - t1.login_date))::integer/60
If you need to cast:
select extract (epoch from (t1.logout_date::timestamp - t1.login_date::timestamp))::integer/60
or see the to_timestamp
function for custom string parsing: http://www.postgresql.org/docs/9.4/static/functions-formatting.html