EXTRACT

The EXTRACT function in BigQuery will return a specific part of a DATE, DATETIME or TIMESTAMP.

EXTRACT(part FROM expression)

Where expression is a DATE, part values can be:

• DAYOFWEEK Returns a number 1-7 with Sunday being the first day of the week.

• DAY

• DAYOFYEAR

• WEEK

• WEEK(<WEEKDAY>) WEEKDAY defines the start of the week, values can be SUNDAY, MONDAY etc

• ISOWEEK

• MONTH

• QUARTER

• YEAR

• ISOYEAR

Returns: INT64

Where expression is a DATETIME, part values can be all of the parts used with DATE (as listed above) plus:

• DATE

• TIME

• MICROSECOND

• MILLISECOND

• SECOND

• MINUTE

• HOUR

Returns: DATE for DATE part and TIME for TIME part.

Where expression is a TIMESTAMP, part values can be all of the parts used with DATE and DATETIME (as listed above) plus:

• DATETIME

Returns: DATETIME for DATETIME part.

WITH table AS (
  SELECT DATETIME(TIMESTAMP '2021-01-05 00:00:00+00', 'UTC') AS datetime
)
SELECT
  datetime,
  EXTRACT(WEEK FROM datetime) AS week_sunday,
  EXTRACT(WEEK(MONDAY) FROM datetime) AS week_monday
FROM table

When expression is a TIMESTAMP you an add an optional argument to specify the timezone of the output:

WITH table AS (
  SELECT
    CAST('2021-01-05 00:00:00+00' AS TIMESTAMP) AS datetime
)
SELECT
  datetime,
  EXTRACT(HOUR FROM datetime AT TIME ZONE 'America/Los_Angeles') AS hour_in_LA,
  EXTRACT(HOUR FROM datetime) AS hour
FROM
  table

• Dates and Times in BigQuery