What is the purpose of the SQL function DATEDIFF?

The DATEDIFF function in SQL is used to calculate the difference between two dates. It can calculate the number of days, hours, minutes, seconds, etc. between two dates. The syntax of the DATEDIFF function is as follows:

DATEDIFF(unit, start_date, end_date)

The unit parameter specifies the time interval unit to be calculated, which can be one of the following values: year, quarter, month, day, hour, minute, second. The start_date and end_date parameters specify the start and end dates for the calculation. For example, to calculate the number of days between two dates, you can use the following statement:

SELECT DATEDIFF(day, '2021-01-01', '2021-01-10');

This will return 9, indicating that there are 9 days between January 1, 2021 and January 10, 2021. The DATEDIFF function is very useful in SQL and can be used for various calculations and queries, such as calculating the time interval between two events or filtering data within a specified time range.