How to subtract 30 days from the current datetime in mysql?

Question

How do I subtract 30 days from the current datetime in mysql?

SELECT * FROM table
WHERE exec_datetime BETWEEN DATEDIFF(NOW() - 30 days) AND NOW();
         


        

Answer 1

Let's not use NOW() as you're losing any query caching or optimization because the query is different every time. See the list of functions you should not use in the MySQL documentation.

In the code below, let's assume this table is growing with time. New stuff is added and you want to show just the stuff in the last 30 days. This is the most common case.

Note that the date has been added as a string. It is better to add the date in this way, from your calling code, than to use the NOW() function as it kills your caching.

SELECT * FROM table WHERE exec_datetime >= DATE_SUB('2012-06-12', INTERVAL 30 DAY);

You can use BETWEEN if you really just want stuff from this very second to 30 days before this very second, but that's not a common use case in my experience, so I hope the simplified query can serve you well.