Date periods overlapping

I found this sitting in drafts, short post regarding period overlapping.
With simple logic we can eliminate the OR conditions related to all possible combinations.

The post:

The possible four cases where period overlap can occur are:

case 1:


case 2:


case 3:


case 4:


One way we can determine the overlapping periods is if we use OR conditions for all cases, e.g.:

(start_date_1 between start_date_2 and end_date_2) -- case 2/case_3
(end_date_1 between start_date_2 and end_date_2) -- case 1/case 3
(start_date_2 between start_date_1 and start_date_2) -- case 4


If you are familiar with De Morgan’s laws (from school 🙂 ) then:

“not (A and B)” is the same as “(not A) or (not B)”
“not (A or B)” is the same as “(not A) and (not B)”.

With this implemented, we can get the following condition:

(start_date1 <= end_date2 AND end_date1 >= start_date2)