Extract函数

 Oracle/PLSQL: Extract Function

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In Oracle/PLSQL, the extract function extracts a value from a date or interval value.

The syntax for the extract function is:

EXTRACT (
{ YEAR | MONTH | DAY | HOUR | MINUTE | SECOND }
| { TIMEZONE_HOUR | TIMEZONE_MINUTE }
| { TIMEZONE_REGION | TIMEZONE_ABBR }
FROM { date_value | interval_value } )

You can only extract YEAR, MONTH, and DAY from a DATE.
You can only extract TIMEZONE_HOUR and TIMEZONE_MINUTE from a timestamp with a time zone datatype.

For example:

extract(YEAR FROM DATE '2003-08-22') would return 2003
extract(MONTH FROM DATE '2003-08-22') would return 8
extract(DAY FROM DATE '2003-08-22') would return 22