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This documentation is related to an older version of Firebolt. For the most current documentation, see Firebolt documentation.

DATE_TRUNC

You are looking at the documentation for Firebolt’s redesigned date and timestamp types. These types were introduced in DB version 3.19 under the names PGDATE, TIMESTAMPNTZ and TIMESTAMPTZ, and synonyms DATE, TIMESTAMP and TIMESTAMPTZ made available in DB version 3.22.

If you worked with Firebolt before DB version 3.22, you might still be using the legacy date and timestamp types. Determine which types you are using by executing the query SELECT EXTRACT(CENTURY FROM DATE '2023-03-16');. If this query returns a result, you are using the redesigned date and timestamp types and can continue with this documentation. If this query returns an error, you are using the legacy date and timestamp types and can find legacy documentation here, or instructions to use the new types here.

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

The functions works with new PGDATE, TIMESTAMPTZ, and TIMESTAMPNTZ data types. If you are using legacy DATE and TIMESTAMP data types, see DATE_TRUNC (legacy).

Syntax 

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

Parameters

Parameter Description Supported input types
<time_unit> The time unit precision to truncate to. 'microseconds', 'milliseconds', 'second', 'minute', 'hour', 'day', 'week', 'month', 'quarter', 'year', 'decade', 'century', 'millennium' (quoted)
<expression> An expression to be truncated. DATE, TIMESTAMP, TIMESTAMPTZ
<time_zone> Optional, the time zone to use for TIMESTAMPTZ values. A string literal such as 'Europe/Berlin'

Return Types

Same as the input data type (<time_unit>)

Remarks

When the <expression> value is of type TIMESTAMPTZ, truncation is performed after converting the value from Unix time 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, DATE_TRUNC uses the time zone specified in the session’s <time_zone> setting, but the optional <time_zone> argument can be provided to use a different time zone.

Firebolt throws an error if the <time_zone> argument is provided for a source of type DATE or TIMESTAMP.

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);

Example 

SELECT DATE_TRUNC('century', DATE '1996-09-03');  --> 1901-01-01
SELECT DATE_TRUNC('hour', TIMESTAMP '1996-09-03 11:19:42.123');  --> 1996-09-03 11:00:00

SET time_zone = 'US/Pacific';
SELECT DATE_TRUNC('week', TIMESTAMPTZ '1996-09-03 11:19:42.123 Europe/Berlin');  --> 1996-09-02 00:00:00-07
SELECT DATE_TRUNC('week', TIMESTAMPTZ '1996-09-03 11:19:42.123 Europe/Berlin', 'Europe/Berlin');  --> 1996-09-01 15:00:00-07