8.4. Date and Time Functions - 8.4.3. EXTRACT() - 《Firebird 2.5 Language Reference》

8.4.3. EXTRACT()

8.4.3. `EXTRACT()`

Available in

DSQL, ESQL, PSQL

Syntax

EXTRACT (<part> FROM <datetime>)
<part> ::=
    YEAR | MONTH | WEEK
  | DAY | WEEKDAY | YEARDAY
  | HOUR | MINUTE | SECOND | MILLISECOND
<datetime> ::= a DATE, TIME or TIMESTAMP expression

Table 143. `EXTRACT` Function Parameters
Parameter	Description
part	Date/time unit
datetime	An expression of the `DATE`, `TIME` or `TIMESTAMP` type

Result type

SMALLINT or NUMERIC

Description

Extracts and returns an element from a DATE, TIME or TIMESTAMP expression. This function was already added in InterBase 6, but not documented in the Language Reference at the time.

Returned Data Types and Ranges

The returned data types and possible ranges are shown in the table below. If you try to extract a part that isn’t present in the date/time argument (e.g. SECOND from a DATE or YEAR from a TIME), an error occurs.

Table 144. Types and ranges of `EXTRACT` results
Part	Type	Range	Comment
`YEAR`	`SMALLINT`	1-9999
`MONTH`	`SMALLINT`	1-12
`WEEK`	`SMALLINT`	1-53
`DAY`	`SMALLINT`	1-31
`WEEKDAY`	`SMALLINT`	0-6	0 = Sunday
`YEARDAY`	`SMALLINT`	0-365	0 = January 1
`HOUR`	`SMALLINT`	0-23
`MINUTE`	`SMALLINT`	0-59
`SECOND`	`NUMERIC(9,4)`	0.0000-59.9999	includes millisecond as fraction
`MILLISECOND`	`NUMERIC(9,1)`	0.0-999.9	broken in 2.1, 2.1.1

`MILLISECOND`

Description

Firebird 2.1 and up support extraction of the millisecond from a TIME or TIMESTAMP. The datatype returned is NUMERIC(9,1).

If you extract the millisecond from CURRENT_TIME, be aware that this variable defaults to seconds precision, so the result will always be 0. Extract from CURRENT_TIME(3) or CURRENT_TIMESTAMP to get milliseconds precision.

`WEEK`

Description

Firebird 2.1 and up support extraction of the ISO-8601 week number from a DATE or TIMESTAMP. ISO-8601 weeks start on a Monday and always have the full seven days. Week 1 is the first week that has a majority (at least 4) of its days in the new year. The first 1-3 days of the year may belong to the last week (52 or 53) of the previous year. Likewise, a year’s final 1-3 days may belong to week 1 of the following year.

Be careful when combining WEEK and YEAR results. For instance, 30 December 2008 lies in week 1 of 2009, so extract(week from date ‘30 Dec 2008’) returns 1. However, extracting YEAR always gives the calendar year, which is 2008. In this case, WEEK and YEAR are at odds with each other. The same happens when the first days of January belong to the last week of the previous year.

Please also notice that WEEKDAY is not ISO-8601 compliant: it returns 0 for Sunday, whereas ISO-8601 specifies 7.