How to calculate the difference between two dates using the DATEDIFF() function?

DATEDIFF(from_date, to_date) is a MySQL built-in function that calculates the difference from one date to another. For example:

SELECT DATEDIFF('2022-12-31 23:59:59','2022-12-30');
  -- +----------------------------------------------+
  -- | DATEDIFF('2022-12-31 23:59:59','2022-12-30') |
  -- +----------------------------------------------+
  -- |                                            1 |
  -- +----------------------------------------------+

SELECT DATEDIFF('2022-11-30 23:59:59','2022-12-31');
  -- +----------------------------------------------+
  -- | DATEDIFF('2022-11-30 23:59:59','2022-12-31') |
  -- +----------------------------------------------+
  -- |                                          -31 |
  -- +----------------------------------------------+

Reference information of the DATEDIFF() function:

DATEDIFF(from_date, to_date): int
  Subtracts to_date from from_date and returns the difference in days.
  Arguments are date or date-and-time expressions and only the date parts
  are used in the calculation.

Arguments, return value and availability:
  from_date: Required. The date to be subtracted from.
  to_date: Required. The date to be subtracted.
  int: Return value. The difference in days.
  Available since MySQL 4.

⇒ DATE_ADD() - Adding Date/Time Interval

⇐ DATE() - Extracting Date

⇑ MySQL Functions on Date and Time

⇑⇑ MySQL Function References