Sometime you have to select values from your SQL Server
table if record has null value or not. For example I have below table in design
mode and with records.

Image 1.

Image 2.
Now Write Query to Select All records:
SELECT * FROM
EMPLOYEE

Image 3.
Now if you want to fetch those records who have EXPERIENCE as null. You
will want to write your query like below:
SELECT * FROM
EMPLOYEE WHERE EXPERIENCE = NULL
SELECT * FROM
EMPLOYEE WHERE EXPERIENCE = 0
SELECT * FROM
EMPLOYEE WHERE EXPERIENCE < 1

Image 4.
Now write your query like below:
SELECT * FROM
EMPLOYEE WHERE EXPERIENCE IS NULL

Image 5.
SELECT * FROM
EMPLOYEE WHERE ISNULL(EXPERIENCE,0)=0

Image 6.
Now query to select All records where Experience is Not
Null
SELECT * FROM
EMPLOYEE WHERE EXPERIENCE IS NOT NULL

Image 7.