People use the TRUNCATE command in SQL Server to “instantly” delete the contents of a table.
TRUNCATE TABLE MyDatabase.Employees; GO
It is considered a better way to delete the contents of a table than the DELETE statement, because the DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row. The TRUNCATE statement simply deallocates the data pages and logs that event in the transaction log. This could prevent issues with your transaction log growing during delete actions.
What you may not realize is this also resets the identity column as well. Microsoft says:
If the table contains an identity column, the counter for that column is reset to the seed value defined for the column. If no seed was defined, the default value 1 is used. To retain the identity counter, use DELETE instead.
Another way to reset the identify column seed value, after to have deleted the records in the table, is to execute this command:
DBCC CHECKIDENT ('MyDatabase.Employees', RESEED, 0); GO
This will reset the seed value if the table is empty.