How to check if two date ranges overlap in mysql?

Question

In mysql, how can I check if two date ranges overlap?

I have this:

Note: We have that p.date_started <= p.date_finished but dateA

Answer 1

You can cover all date overlapping cases even when to-date in database can possibly be null as follows:

SELECT * FROM `tableName` t
WHERE t.`startDate` <= $toDate
AND (t.`endDate` IS NULL OR t.`endDate` >= $startDate);

This will return all records that overlaps with the new start/end dates in anyway.