Orders: List Orders With Customer Names (INNER JOIN)

SQL coding challenge · Difficulty: easy · Topic: Joins · +50 XP

Problem

The billing system generates invoices that need each order linked to the customer's name. Only include orders with a valid matching customer.

Tables

Table: customers

| customer_id | customer_name | status | register_date |
| --- | --- | --- | --- |
| 1 | Krishna | Active | 2024-05-01 |
| 2 | Parvati | Active | 2024-05-10 |
| 3 | Atul | Inactive | 2024-04-01 |
| 4 | Pinki | Active | 2024-05-20 |
| 5 | Sudheer | Active | 2024-04-01 |

Table: orders

| order_id | customer_id | order_date | order_amount |
| --- | --- | --- | --- |
| 101 | 1 | 2024-05-01 | 500 |
| 102 | 1 | 2024-05-05 | 800 |
| 103 | 1 | 2024-05-10 | 200 |
| 104 | 2 | 2024-05-02 | 1200 |
| 105 | 2 | 2024-05-08 | 600 |
| 106 | 3 | 2024-05-03 | 300 |
| 107 | 4 | 2024-05-04 | 200 |
| 108 | 4 | 2024-05-09 | 400 |
| 109 | 4 | 2024-05-11 | 700 |
| 110 | 4 | 2024-05-12 | 350 |
| 111 | 4 | 2024-05-13 | 450 |
| 112 | 4 | 2024-05-14 | 600 |
| 113 | 1 | 2024-06-05 | 1000 |
| 114 | 2 | 2024-06-10 | 900 |

Expected Output

| order_id | order_date | customer_name |
| --- | --- | --- |
| 101 | 2024-05-01 | Krishna |
| 102 | 2024-05-05 | Krishna |
| 103 | 2024-05-10 | Krishna |
| 104 | 2024-05-02 | Parvati |
| 105 | 2024-05-08 | Parvati |
| 106 | 2024-05-03 | Atul |
| 107 | 2024-05-04 | Pinki |
| 108 | 2024-05-09 | Pinki |
| 109 | 2024-05-11 | Pinki |
| 110 | 2024-05-12 | Pinki |
| 111 | 2024-05-13 | Pinki |
| 112 | 2024-05-14 | Pinki |
| 113 | 2024-06-05 | Krishna |
| 114 | 2024-06-10 | Parvati |

• Return: order_id, order_date, customer_name
• Only orders with a matching customer (INNER JOIN)
• Sort by order_id ascending

Success Criteria

• Your query returns three columns: order_id, order_date, customer_name.
• Only orders whose customer_id matches a real customer appear.
• The rows match the Expected Output exactly, with no extras.
• Row order is not graded, so an ORDER BY here is for your own reading.

What this SQL challenge teaches you

“Orders: List Orders With Customer Names (INNER JOIN)” is a easy-level SQL challenge focused on Joins. Working through it gives you hands-on practice with INNER JOIN, JOIN — the kind of transformation you are asked to write in real data engineering work and in technical interviews. You can solve it directly in the browser: the dataset is pre-loaded, so you write the query or DataFrame code, run it, and compare your output against the expected result immediately.

Concepts covered

• INNER JOIN
• JOIN

How to approach it

If you get stuck, work through these steps in order before looking at a full solution — each one narrows the problem down:

1. The order rows and the customer names live in different tables, so the two have to be matched on the column they share.
2. An INNER JOIN on customer_id keeps only the orders that have a matching customer, which is exactly what is asked for.
3. Select order_id and order_date from orders and customer_name from customers. An order whose customer is missing should simply not appear.

Where this comes up

Variations of this problem have been reported in interviews at Amazon, Flipkart, Infosys, TCS. Interviewers use it to check whether you can express the logic cleanly and reason about correctness on edge cases such as ties, nulls and empty groups.

How to practise it on PySpark.in

Open the challenge, write your SQL query in the editor and press Run to execute it against the sample dataset. Submitting checks your output against every test case, including hidden ones, so you find out straight away whether your logic holds up. You can retry as often as you like, and each solved challenge adds to your XP.

Related SQL challenges

• Find Customers Missing from New Table
• Customers With at Least One Order
• Customers Who Have Never Placed an Order
• Count Orders Per Customer Including Zero
• Total Amount Spent Per Customer (With Zero)
• Find Employees in the HR Department

Helpful resources

• Practice this topic
• All SQL practice questions
• Open the notebook

Frequently asked questions

Do I need to install Spark or a database to solve this?

No. The SQL environment runs in your browser with the sample data already loaded, so there is nothing to install or configure.

Is this challenge free?

Yes - the problem, the sample dataset, the hints and unlimited test runs are free.

What level is it?

It is rated easy and covers Joins.

Solve this challenge free on PySpark.in