Extraction function 
An extraction (extraction_function) is a function that extracts parts of a date value, time value, or time stamp value or that calculates a date, time, or time stamp value.
Syntax
<extraction_function> ::=
DATE (
<expression>
)
| DAY (
<date_or_timestamp_expression> )
| HOUR (
<time_or_timestamp_expression> )
| MICROSECOND (
<expression> )
| MINUTE (
<time_or_timestamp_expression> )
| MONTH (
<date_or_timestamp_expression> )
| SECOND (
<time_or_timestamp_expression> )
| TIME (
<expression> )
| TIMESTAMP (
<expression>[, <expression> ] )
| YEAR (
<date_or_timestamp_expression> )
<date_or_timestamp_expression> ::= <expression>
<time_or_timestamp_expression> ::= <expression>
Examples
SQL Tutorial, 
Date and Time
Calculations
Explanation
When used in a function, the argument date_or_timestamp_expression must supply a date, a time stamp, or an alphanumeric value that matches the current date or time stamp format.
When used in a function, the argument time_or_timestamp_expression must supply a time, a time stamp value, or an alphanumeric value that matches the current time or time stamp format.
Date and time values are available in a variety of date and time formats (ISO, USA, EUR, JIS, INTERNAL).
See also: