I'm going to share how to calculate the date intervals between two dates like calculating 1 month before, two weeks before etc. You can do this using "DATE_SUB" mysql function. Find the below example to get proper understanding, it is an example of getting all medicines which are going to expire in next two weeks:
$sql = "SELECT * FROM `products` p WHERE CURRENT_TIMESTAMP >= DATE_SUB(FROM_UNIXTIME(p.medicine_expiry_date, '%Y-%m-%d 00:00:00'), INTERVAL 2 WEEK)";
Use this function wherever such requirement comes and it will solve easily.
