Customers Who Never Order SQL Challenge - Oracle Solution

1. Introduction

This blog post explores a frequent SQL query challenge in Oracle databases – finding customers who have never made an order. Such queries are essential for business analysis and customer engagement strategies.

Problem

The task is to write an Oracle SQL query that identifies customers from a customer table who have no corresponding entries in an order table.

Database Table:

Customers Table:

Id	Name
1	Alice
2	Bob

Orders Table:

OrderId	CustomerId
1001	1

3. Oracle Solution

SELECT Name
FROM Customers
WHERE Id NOT IN (SELECT CustomerId FROM Orders);

Output:

Name
Bob

Explanation:

1. The query selects names from the Customers table.

2. It uses a NOT IN subquery to exclude customers who have made orders.

3. The subquery checks the Orders table for customer IDs.

4. Customers whose IDs are not found in the Orders table are identified as those who have never placed an order.