Question

I run the following in Rails:

coe = trackers.where(:trackable_type => "Mailing").count(:group => 'DATE(created_at)')

which returns a hash with the items nicely grouped.

However I want to group not by date only by date but by the hour, but not the minutes or seconds.

How can I run this query so all the heavy lifting is done by Postgresql and not convert after I get the data set back?

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My mistake I want to group by Date and Hour. Sorry for the confusion.

Answer 1

It sounds like you want the date_trunc() function:

http://www.postgresql.org/docs/current/interactive/functions-datetime.html#FUNCTIONS-DATETIME-TABLE