SQL NULL Value Explained: How to Use IS NULL & IS NOT NULL

SQL NULL Values: Main Tips

• This value defines lost data.
• Tables already contain NULL values.
• NULL is handled not like other values.

SQL Working with NULL Values

Below there is a table called "People":

Hypothetically the "Adress" column is optional. Then when you write a data record without a value assigned it will receive NULL.

Testing is unavailable using default operators, that's why we use IS NULL/IS NOT NULL.

IS NULL: Example

To select NULL data records we use IS NULL operator:

SELECT col_names
FROM tbl_name
WHERE col_name IS NULL;

SELECT Name, Unit 
FROM Products 
WHERE Unit_On_Order IS NULL;

IS NOT NULL: Example

To select data records with no NULL values we use IS NOT NULL operator:

SELECT col_names
FROM tbl_name
WHERE col_name IS NOT NULL;

SELECT Name, Price 
FROM Products 
WHERE Unit_On_Order IS NOT NULL;