Write a query to retrieve customers who do not have an email.

Objective:

Write a SQL query to retrieve customers who do not have an email.

Step 1: Create the customers Table

Let’s first create a customers table with the following fields:

CREATE TABLE customers (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    email VARCHAR(100)
);

Step 2: Insert Dummy Data

Let’s insert some sample records, including some without emails (i.e., NULL values):

INSERT INTO customers (id, name, email) VALUES
(1, 'John Doe', 'john@example.com'),
(2, 'Jane Smith', NULL),
(3, 'Alice Johnson', 'alice@example.com'),
(4, 'Bob Brown', NULL),
(5, 'Mike Davis', 'mike.davis@example.com');

Step 3: Write the SQL Query

Now, to retrieve customers who do not have an email, we need to filter the records where the email is NULL.

SELECT * FROM customers
WHERE email IS NULL;

Output (Result)

Why IS NULL instead of = NULL?

In SQL, to check for NULL values you must use:

• IS NULL — to find rows where a column is null
• IS NOT NULL — to find rows where a column has a value

Because = NULL does not work (it always evaluates to unknown).