SQL Server NULLABLE column vs SQL COUNT() function

Question

Could someone help me understand something? When I can, I usually avoid (*) in an SQL statement. Well, today was payback. Here is a scenario:

CREATE TABLE Tbl (Id INT IDENTITY(1, 1) PRIMARY KEY, Name NVARCHAR(16))

INSERT INTO Tbl VALUES (N'John')
INSERT INTO Tbl VALUES (N'Brett')
INSERT INTO Tbl VALUES (NULL)

I could count the number of records where Name is NULL as follows:

SELECT COUNT(*) FROM Tbl WHERE Name IS NULL

While avoiding the (*), I discovered that the following two statements give me two different results:

SELECT COUNT(Id) FROM Tbl WHERE Name IS NULL
SELECT COUNT(Name) FROM Tbl WHERE Name IS NULL

The first statement correctly return 1 while the second statement yields 0. Why or How?

Answer 1

That's because

The COUNT(column_name) function returns the number of values (NULL values will not be counted) of the specified column

so when you count Id you get expected result, while counting Name no, but the answer provided by query is correct