How does SQL Server calculate the difference between two dates?

2 years ago
Benjamin Taylor
2 minutes

In SQL Server, you can use the DATEDIFF function to calculate the difference between two dates. The syntax of the DATEDIFF function is as follows:

Find the difference in time between two dates using the DATEDIFF function.

datepart is the unit specified for calculating the difference, which can be one of the following values:

  1. year: a particular period of time measured in twelve months.
  2. quarter: a period of three months
  3. month: a period of time consisting of approximately 30 days, typically divided into four weeks.
  4. number of days
  5. hour: a unit of time equal to 60 minutes
  6. minute: unit of time equal to sixty seconds
  7. The second is a unit of time.

Start date and end date are two dates that need to be calculated for the difference.

Here is an example of calculating the number of days between two dates:

DECLARE @StartDate DATE = '2021-01-01'
DECLARE @EndDate DATE = '2021-01-31'

SELECT DATEDIFF(day, @StartDate, @EndDate) AS DateDiff

In this example, the calculation involves finding the number of days between January 1st, 2021 and January 31st, 2021. The result will be 30, indicating a 30-day difference between the two dates.

Please note that the DATEDIFF function calculates the difference in whole numbers and does not consider the precision of time.

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