The simplest way to group by:
- day of the week
- hour of the day
- and more
Supports PostgreSQL and MySQL
Run this SQL
For MySQL, time zone support must be installed on the server.
mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql
Groupdate.sql creates SQL functions, which are stored by the database. You can use these functions with any ORM or without one. Times stored in your database are assumed to be UTC (this is the default for frameworks like Rails).
Group by day
SELECT gd_day(created_at, 'America/Los_Angeles') AS day, COUNT(*) FROM users GROUP BY day; -- result day | count ------------+------- 2013-04-11 | 145 2013-04-12 | 65 2013-04-13 | 293
Group by week
SELECT gd_week(created_at, 'America/Chicago') AS week, COUNT(*) FROM users GROUP BY week; -- result week | count ------------+------- 2013-05-05 | 1327 2013-05-12 | 3432 2013-05-19 | 673
Weeks start on Sunday by default
Group by dynamic period
SELECT gd_period('day', created_at, 'America/Los_Angeles') AS period, COUNT(*) FROM users GROUP BY period;
Here’s the complete list of functions. All are prefixed with
gd_ to prevent conflicts with MySQL functions.
A list of time zones can be found here.
With PostgreSQL, the time zone is optional.
SELECT gd_day(created_at) AS day, COUNT(*) FROM users GROUP BY day;
The default is UTC. Change this to your preferred time zone by running:
CREATE OR REPLACE FUNCTION gd_time_zone() RETURNS text AS $$ SELECT 'America/Los_Angeles'::text; $$ LANGUAGE SQL IMMUTABLE;
Set the day weeks start. The default is Sunday.
For PostgreSQL, run:
CREATE OR REPLACE FUNCTION gd_week_start() RETURNS int AS $$ SELECT 6; -- mon=0, tue=1, wed=2, thu=3, fri=4, sat=5, sun=6 $$ LANGUAGE SQL IMMUTABLE;
For MySQL, run:
START TRANSACTION; DROP FUNCTION IF EXISTS gd_week_start; CREATE FUNCTION gd_week_start() RETURNS INT DETERMINISTIC RETURN 6; -- mon=0, tue=1, wed=2, thu=3, fri=4, sat=5, sun=6 COMMIT;
Run this SQL
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