In MySQL, If I have a list of date ranges (range-start and range-end). e.g.
10/06/1983 to 14/06/1983 15/07/1983 to 16/07/1983 18/07/1983 to 18/07/1983
CREATE FUNCTION overlap_date(s DATE, e DATE, a DATE, b DATE) RETURNS BOOLEAN DETERMINISTIC RETURN s BETWEEN a AND b or e BETWEEN a and b or a BETWEEN s and e;