SQL Server Date Function DATEDIFF()

The DATEDIFF() function in SQL Server is used to calculate the difference between two date or datetime values. It takes three arguments: the unit of time to measure the difference in, the starting date or datetime value, and the ending date or datetime value.

The syntax of the DATEDIFF() function is as follows:

DATEDIFF(unit, start_date, end_date)

Here's an example of how to use the DATEDIFF() function in a SQL query to calculate the number of days between two dates:

SELECT DATEDIFF(day, '2022-02-28', '2022-03-31');

This query will return the integer value 31, which is the number of days between the two dates.

In this example, the unit is "day" since we want to measure the difference in days between the two dates. The start_date is "2022-02-28", which is the earlier date. The end_date is "2022-03-31", which is the later date.

Note that the DATEDIFF() function is specific to SQL Server and the syntax and date format it supports may vary slightly depending on the system. Additionally, the unit of time used to measure the difference can be changed to other units, such as months or years, by using different unit values.