Scalar Functions

date_trunc(‘interval’, [‘timezone’,] timestamp)

The date_trunc function truncates a timestamp to a given interval for a specific timezone.

Valid intervals are:

  • second
  • minute
  • hour
  • day
  • week
  • month
  • quarter
  • year

Valid values for timezone are either the name of a time zone (for example ‘Europe/Vienna’) or the UTC offset of a time zone (for example ‘+01:00’). To get a complete overview of all possible values take a look at the available time zones supported by Joda-Time.

The following example shows how to use the date_trunc function to generate a day based histogram in the Europe/Moscow timezone:

cr> select
... date_trunc('day', 'Europe/Moscow', date) as day,
... count(*) as num_locations
... from locations
... group by date_trunc('day', 'Europe/Moscow', date)
... order by date_trunc('day', 'Europe/Moscow', date)
+---------------+---------------+
| day           | num_locations |
+---------------+---------------+
| 308523600000  | 4             |
| 1367352000000 | 1             |
| 1373918400000 | 8             |
+---------------+---------------+
SELECT 3 rows in set (... sec)

If the time zone is not specified, truncation is based on UTC time:

cr> select date_trunc('day', date) as day, count(*) as num_locations
... from locations
... group by date_trunc('day', date)
... order by date_trunc('day', date)
+---------------+---------------+
| day           | num_locations |
+---------------+---------------+
| 308534400000  | 4             |
| 1367366400000 | 1             |
| 1373932800000 | 8             |
+---------------+---------------+
SELECT 3 rows in set (... sec)

Note

Currently scalar functions, such as date_trunc, can only be used in the GROUP BY and ORDER BY clauses.