How many users added per day, including rows for days with no registrations

README.markdown

Wanted to make a table of net user growth for further analysis in some spreadsheet or other.

The obvious query (in the snippet it is the inner query) only generates rows for days with at least one registration. For this to make nice charts, we need to add blank rows with the missing dates. The set returning function generate_series creates the equivalent of a temporary table to join with.

snippet.sql

select generate_series date, users_added 
from 
    generate_series('2013-03-05'::timestamp, '2014-10-29', '1 day') 
    left join (
        select date_trunc('day', date_joined) date_joined, count(id) users_added 
        from registration_registereduser 
        where is_active 
        group by 1
    ) xs on generate_series = date_joined 
order by 1;