如何比较php和sql中的日期？

Question

I want to make a notification system. Shortly.. to compare two dates, the only problem is that i want to compare the months. to see if a month or two have passed from last notification.

i want to use one or two months from an entry in a mysql database.

the client must select when the notification must come, one or two months.

thank you, Sebastian

Answer 1

Your statement should look like this:

SELECT * FROM table WHERE date_column + INTERVAL 1 MONTH >= NOW()

You add 1 (or 2) month to the date of the column in which the date is stored and compare it to the current time "NOW()".

That works with DATE, DATETIME and TIMESTAMP columns.

Answer 2

You can compare months of two datetime columns inside of MySQL.

The only computer-related shortcoming of saying "a month has passed" is that a "month" is an arbitrary unit of time; some have 30 days, others have 31 and one even has 28. I would suggest using the logic of "30 days has passed" because it is based on a set unit of time, a day, which is 86,400 seconds long (with negligible error of course).