SQL Server : why doesn't this query return NULL values?

Question

I have a table with one column named value, of type int, and 4 rows in it:

20
50
NULL
0

Why does this query return 20 and 50 only? I need NULL values, too.

SELECT * 
FROM dbo.myTable
WHERE value != 0

Answer 1

In SQL, NULL is a special value, nothing can ever be equal to or not equal to it. In fact, NULL doesn't even equal itself. When searching for null values, you must use the IS operator. So you need to change your query to include them:

SELECT * 
FROM dbo.myTable
WHERE value !=0
OR value IS NULL

Answer 2

You can also replace null for sth else what is not a zero using isnull or coalesce

SELECT * 
FROM dbo.myTable
WHERE ISNULL(value,1) <> 0