COUNT of DISTINCT Rows in SQL Server

SQL Server does not support COUNT(DISTINCT *). For example, the below query fails.

SELECT COUNT(DISTINCT *) FROM Employees

The error message generated is:

Incorrect syntax near '*'

Instead, use the below query:

SELECT COUNT(*) FROM (SELECT DISTINCT * FROM Employees) Emp

Note: This is specifically useful when you want 'DISTINCT *' - without coloumn name(s)