find days from two days mysql code example

Example 1: mysql datediff days

#Get date diff in days
select DATEDIFF('2020-04-13', '2020-04-20');#returns -7
select DATEDIFF('2020-04-20', '2020-04-13');#returns  7

Example 2: mysql filter based on datediff

SELECT *
FROM myTable
WHERE birthdate >= 'date1' AND death <= 'date2' AND age > 17 AND age < 55;