The SQL **DATEDIFF** function is a built-in function in SQL that calculates the difference between two dates or times. It returns an integer value that represents the number of specified date or time units between two dates or times.

## Syntax

The syntax for the **DATEDIFF** function is as follows:

DATEDIFF(datepart, startdate, enddate)

Where datepart is a string that specifies the unit of time you want to use for the calculation (e.g., year, quarter, month, day, hour, minute, second), startdate is the starting date or time, and enddate is the ending date or time.

### Examples

For example, if you want to calculate the number of days between two dates, you can use the following SQL query:

SELECT DATEDIFF(day, '2022-01-01', '2022-02-01') AS DayDiff;

This query will return the number of days between January 1, 2022, and February 1, 2022, which is 31.

Similarly, you can use the **DATEDIFF** function to calculate the difference between two times. For example, if you want to calculate the number of hours between two times, you can use the following SQL query:

SELECT DATEDIFF(hour, '2022-01-01 12:00:00', '2022-01-01 14:30:00') AS HourDiff;

This query will return the number of hours between 12:00 PM and 2:30 PM on January 1, 2022, which is 2.

In addition to calculating the difference between two dates or times, the **DATEDIFF** function can also be used to perform date and time arithmetic. For example, you can add or subtract a number of specified date or time units from a date or time using the DATEDIFF function.

Overall, the **SQL DATEDIFF function** is a useful tool for working with dates and times in SQL, and it can help you perform a variety of calculations and operations on date and time data.