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Truncates a value (<expression>) of type DATE, TIMESTAMP, or TIMESTAMPTZ to the selected precision (<time_unit>).

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Syntax

DATE_TRUNC(<time_unit>, <expression> [, <time_zone> ])

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Parameters

ParameterDescription
<time_unit>A TEXT literal with the time unit precision to truncate to. Must be one of microsecond, millisecond, second, minute, hour, day, week, month, quarter, year, decade, century or millennium.
<expression>A value expression evaluating to the DATE, TIMESTAMP, or TIMESTAMPTZ value that should be truncated.
<time_zone>An optional TEXT literal giving a time zone name.

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Return Type

DATE if <expression> has type DATE, TIMESTAMP if <expression> has type TIMESTAMP, TIMESTAMPTZ if <expression> has type TIMESTAMPTZ.

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Remarks

Truncation of TIMESTAMPTZ values is performed after conversion to local time in a particular time zone. For instance, truncation to ‘day’ produces a TIMESTAMPTZ that is midnight in that time zone. By default, the function uses the time zone specified in the session’s time_zone setting. Alternatively, if the optional <time_zone> argument is provided, the function uses that time zone. Firebolt raises an error if the optional <time_zone> argument is provided for an <expression> evaluating to DATE or TIMESTAMP. Firebolt also raises an error if one attempts to truncate a value expression of type DATE to microsecond, millisecond, second, minute, or hour. The DATE_TRUNC function can be used in the PARTITION BY clause of CREATE TABLE commands. 
CREATE DIMENSION TABLE test (
  d DATE,
  t TIMESTAMP
)
PARTITION BY DATE_TRUNC('month', d), DATE_TRUNC('hour', t);

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Example

The following examples truncate DATE and TIMESTAMP values without timezones. You can also truncate TIMESTAMPTZ values. 
SET time_zone = 'US/Pacific';
-- Returns 1996-09-02 00:00:00-07
SELECT DATE_TRUNC('week', TIMESTAMPTZ '1996-09-03 11:19:42.123 Europe/Berlin');  
-- Returns 1996-09-01 15:00:00-07
SELECT DATE_TRUNC('week', TIMESTAMPTZ '1996-09-03 11:19:42.123 Europe/Berlin', 'Europe/Berlin');