MySQL Function Reference

DAYOFMONTH
Returns the day of the month (1-31) for a given date.
MySQL 8.1
DAYOFMONTH(date)
date
The date or datetime value.
Examples
MySQL 8.1
SELECT DAYOFMONTH(date)
FROM Payments;
MySQL 8.1
SELECT member_name,
	DAYOFMONTH(birthday)
FROM FamilyMembers;