EXTRACT¶

语法¶

EXTRACT( <date_or_time_part> FROM <date_interval_time_or_timestamp_expr> )

EXTRACT( <date_or_time_part> , <date_interval_time_or_timestamp_expr> )

实参¶

date_or_time_part

The unit of time. Must be one of the values listed in 支持的日期和时间部分 (for example, month). The value can be a string literal or can be unquoted (for example, 'month' or month).

• 当 date_or_time_part 为 week`（或其任何变体）时，输出由 :ref:`label-week_start 会话参数控制。

• 当 date_or_time_part 为 dayofweek 或 yearofweek`（或其任何变体）时，输出由 :ref:`label-week_of_year_policy 和 WEEK_START 会话参数控制。

有关更多信息（包括示例），请参阅 日历周和工作日。

date_interval_time_or_timestamp_expr

A date, an interval, a time, or a timestamp, or an expression that can be evaluated to one of those data types.

返回¶

返回 NUMBER 数据类型的值。

使用说明¶

• When date_interval_time_or_timestamp_expr is a year-month interval value, the supported date_or_time_part values are year and month.

• When date_interval_time_or_timestamp_expr is a day-time interval value, the supported date_or_time_part values are day, hour, minute, second, and nanosecond.

• Currently, when date_interval_time_or_timestamp_expr is a DATE value, the following date_or_time_part values aren't supported:

  • epoch_millisecond

  • epoch_microsecond

  • epoch_nanosecond

  支持其他 日期和时间部分 （包括 epoch_second）。

示例¶

指定 year 部分，以从时间戳中提取年份：

SELECT EXTRACT(year FROM TO_TIMESTAMP('2024-04-10T23:39:20.123-07:00')) AS YEAR;

+------+
| YEAR |
|------|
| 2024 |
+------+

将 EXTRACT 与 DECODE 函数和 dayofweek 部分一起使用，以返回当前星期几的全称：

SELECT DECODE(EXTRACT(dayofweek FROM SYSTIMESTAMP()),
  1, 'Monday',
  2, 'Tuesday',
  3, 'Wednesday',
  4, 'Thursday',
  5, 'Friday',
  6, 'Saturday',
  7, 'Sunday') AS DAYOFWEEK;

+-----------+
| DAYOFWEEK |
|-----------|
| Thursday  |
+-----------+