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date_trunc

date_trunc

Description​

Truncates a time value based on the specified date part, such as year, day, hour, or minute.

StarRocks also provides the year, quarter, month, week, day, and hour functions for you to extract the specified date part.

Syntax​

DATETIME date_trunc(VARCHAR fmt, DATETIME|DATE datetime)

Parameters​

  • datetime: the time to truncate, which can be of the DATETIME or DATE type. The date and time must exist. Otherwise, NULL will be returned. For example, 2021-02-29 11:12:13 does not exist as a date and NULL will be returned.
  • fmt: the date part, that is, to which precision datetime will be truncated. The value must be a VARCHAR constant. fmt must be set to a value listed in the following table. If the value is incorrect, an error will be returned.

Value

Description

second

Truncates to the second.

minute

Truncates to the minute. The second part will be zero out.

hour

Truncates to the hour. The minute and second parts will be zero out.

day

Truncates to the day. The time part will be zero out.

week

Truncates to the first date of the week that datetime falls in. The time part will be zero out.

month

Truncates to the first date of the month that datetime falls in. The time part will be zero out.

quarter

Truncates to the first date of the quarter that datetime falls in. The time part will be zero out.

year

Truncates to the first date of the year that datetime falls in. The time part will be zero out.

Return value​

Returns a value of the DATETIME type.

If datetime is of the DATE type and fmt is set to hour, minute, or second, the time part of the returned value defaults to 00:00:00.

Examples​

Example 1: Truncate the input time to the minute.

select date_trunc("minute", "2020-11-04 11:12:13");
+---------------------------------------------+
| date_trunc('minute', '2020-11-04 11:12:13') |
+---------------------------------------------+
| 2020-11-04 11:12:00                         |
+---------------------------------------------+

Example 2: Truncate the input time to the hour.

select date_trunc("hour", "2020-11-04 11:12:13");
+-------------------------------------------+
| date_trunc('hour', '2020-11-04 11:12:13') |
+-------------------------------------------+
| 2020-11-04 11:00:00                       |
+-------------------------------------------+

Example 3: Truncate the input time to the first day of a week.

select date_trunc("week", "2020-11-04 11:12:13");
+-------------------------------------------+
| date_trunc('week', '2020-11-04 11:12:13') |
+-------------------------------------------+
| 2020-11-02 00:00:00                       |
+-------------------------------------------+

Example 4: Truncate the input time to the first day of a year.

select date_trunc("year", "2020-11-04 11:12:13");
+-------------------------------------------+
| date_trunc('year', '2020-11-04 11:12:13') |
+-------------------------------------------+
| 2020-01-01 00:00:00                       |
+-------------------------------------------+

Example 5: Truncate a DATE value to the hour. 00:00:00 is returned as the time part.

select date_trunc("hour", "2020-11-04");
+----------------------------------+
| date_trunc('hour', '2020-11-04') |
+----------------------------------+
| 2020-11-04 00:00:00              |
+----------------------------------+