-- counting occurences between dates of different date intervals : to simplify I have a query (MYSQL DB) that give me a table like this

Person | Date_IN | Date_OUT | Structure

During a year a person ENTER and EXIT many times, ENTER and EXIT could be also the same day.
I'd like to count, for a specific day of year, how many person were IN each structure.

The final goal is to have, for a given period (eg. 1st march --> 31st march), the sum of total person for each day for each structure.

Can you help me?
