postgresql - SQL query: Growth of users per month in percentage -


i have easy query calculates number of user registrations per month.

select to_char(created_at, 'yyyy-mm') month, count(user_id) users group month order month desc

what have every month growth in percentages compare previous month.

sql fiddle

select     month, total,     (total::float / lag(total) on (order month) - 1) * 100 growth (     select to_char(created_at, 'yyyy-mm') month, count(user_id) total     users     group month ) s order month;   month  | total |      growth       ---------+-------+------------------  2013-01 |     2 |                   2013-02 |     3 |               50  2013-03 |     5 | 66.6666666666667

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