The DAY function returns the day part of a value. The argument must be a date, timestamp, or a valid character string representation of a date or timestamp that is neither a CLOB nor a LONG VARCHAR. The result of the function is a large integer. If the argument can be null, the result can be null; if the argument is null, the result is the null value.
DAY ( expression )
values day('2005-08-02');
The resulting value is 2.