I'm creating a BloodBank application using c# and MySQL and my trouble right now is that I want to create a query with DATEDIFF() function that can calculate the difference in days between a made donation already and a new one from the same person since the same person can only donate blood 60 days after a previous donation. One of the dates is already in my MYSQL database and the other one will be received from a datepicker in a Window form .Net.
I have problem making the connection between the mysql database row for the current person and the info in the new made donation.
At the end I want to check if the difference between donations from a same person(same name and email in my case) is more than 60 days and in that case he can make a donation again.