# SQL: Find Customers Who Have Gone Quiet with a LEFT JOIN

> A beginner SQL walkthrough in the free DB Fiddle: join a customers table to orders, see why a plain JOIN hides customers who never ordered, and list…

Source: https://learn.ynteractive.com/content/sql-quiet-customers · Updated 2026-10-24 · Free from Stepthrough (https://learn.ynteractive.com)

## Practice it step by step

[Start the free practice](https://learn.ynteractive.com/modules/sql-quiet-customers)

[Take the free module: why it matters, practice and a quick check →](https://learn.ynteractive.com/courses/sql-for-business-reports/3)

You do every step yourself in a practice copy of DB Fiddle. It checks your work as you go, and “Do it for me” finishes any step you get stuck on. Free, about 15 minutes, and nothing touches your real accounts. [Open full screen](https://learn.ynteractive.com/modules/sql-quiet-customers)

Free · Live now · [SQL](https://learn.ynteractive.com/content/course/sql) · [DB Fiddle](https://learn.ynteractive.com/content/tool/db-fiddle) · ~15 min · 17 steps · Beginner

Updated October 24, 2026. Built against the tool’s current screens and checked step by step. [How we check this lesson](https://learn.ynteractive.com/content/about#how-we-check)

A beginner [SQL](https://learn.ynteractive.com/content/glossary/sql) walkthrough in the free DB Fiddle: join a customers table to orders, see why a plain JOIN hides customers who never ordered, and list every quiet account with [LEFT JOIN](https://learn.ynteractive.com/content/glossary/left-join), MAX and HAVING.

## At a glance

| Question | Answer |
| --- | --- |
| What you build | A beginner SQL walkthrough in the free DB Fiddle: join a customers table to orders, see why a plain JOIN hides customers who never ordered, and list every quiet account with LEFT JOIN, MAX and HAVING. |
| Tools | DB Fiddle |
| Time | About 15 minutes, 17 steps in 3 parts |
| Level | Beginner, no coding needed |
| Cost | Free |
| Ways to learn it | [Practice it step by step](https://learn.ynteractive.com/modules/sql-quiet-customers) |

### The 3 parts, in short

1. Make two tables: Click in Schema SQL, Create the customers table, Add two customers, Add three more, and 4 more steps.
2. Join them: Check the customers, Run it, Join customers to their orders, One row per customer, and 1 more step.
3. Find the quiet accounts: Keep customers with no orders, Run it, Keep only the quiet ones, Run the call list.

**Start here first:** [SQL: Build a Monthly Revenue Report from an Orders Table](https://learn.ynteractive.com/content/sql-monthly-revenue-report) (module 1 of SQL)

## What you'll build

Lakeside Office Supply (made up) loses customers quietly: nobody notices that a dental practice stopped ordering until the year-end review. The owner wants a list every Monday of customers with no order since 1 September, with the account manager next to each name so they can call. In this lesson you type two small tables, customers and orders, into [DB Fiddle](https://learn.ynteractive.com/content/tool/db-fiddle), join them, and find the quiet accounts, including one that never ordered at all and a plain JOIN would miss.

Elm Street Law (never ordered), Harbor Accounting (last order 19 August) and Maple Dental (27 August): two calls for Ana and one for Sam. A plain JOIN would have missed Elm Street Law completely. Change the date in the HAVING line and run it every Monday. Do it in DB Fiddle yourself: the lesson page has the checklist.

- Tools: DB Fiddle
- Time: about 15 minutes, 17 steps in 3 chapters
- Level: beginner, no coding needed
- Price: free

## Practice first, then build it for real

Practice copy built from real DB Fiddle screens (db-fiddle.com, MySQL v9, captured 24 October 2026). Every query in it was typed and run there. The shop, its customers and its orders are made up; the ad box on the left is blurred. To build it for real you need your own DB Fiddle account, and some services charge once you use them for real work, so check each tool's current pricing.

## Try it yourself, free

Reading the steps is a start. Doing them is how it sticks. The interactive module walks you through every click in a practice copy of DB Fiddle, checks each step, and never touches your real accounts.

[Start “SQL: Find Customers Who Have Gone Quiet with a LEFT JOIN”](https://learn.ynteractive.com/modules/sql-quiet-customers)

## Step by step: SQL: Find Customers Who Have Gone Quiet with a LEFT JOIN

All 17 steps of the interactive module, in order. In the module you watch each one, then do it yourself in a practice copy that checks your work.

### 1. Make two tables

1. **Click in Schema SQL.** Open **db-fiddle.com** (no account needed) and click inside the left box, **Schema SQL**.
2. **Create the customers table.** A second table this time: every customer and their account manager. Type the code shown below.
   First a customers table: each customer and their account manager.
3. **Add two customers.** Leave a blank line, then type the code shown below.
   Add the first two customers.
4. **Add three more.** Elm Street Law signed up but has never ordered. Keep an eye on it.
   Three more. Elm Street Law signed up but never ordered. Keep an eye on it.
5. **Create the orders table.** Leave a blank line and type the orders table, the same one as in modules 1 and 2.
   Now the orders table, the same as before.
6. **Add the first two orders.** Type the code shown below.
7. **Add three more orders.** Type the code shown below.
   Three more orders.
8. **Add the last three orders.** The last row ends with a semicolon.
   And the last three. The last row ends with a semicolon.

### 2. Join them

9. **Check the customers.** In **Query SQL**, check the new table.
   In Query SQL, list the customers.
10. **Run it.** Click **Run**.
    Run it.
11. **Join customers to their orders.** Five customers, two managers. Now put each customer next to their latest order. Replace the query with three lines. **c** and **o** are short names for the two tables, and **JOIN ... ON** matches each order to the customer with the same name.
    Now join the two tables. Each order is matched to the customer with the same name, and MAX finds the latest order date.
12. **One row per customer.** Add the grouping line.
    [Group by](https://learn.ynteractive.com/content/glossary/group-by) customer and manager.
13. **Run it.** Click **Run**.
    Run it.

### 3. Find the quiet accounts

14. **Keep customers with no orders.** Only four rows: **Elm Street Law is missing**, because a plain JOIN drops anyone with no matching order. That is exactly the customer you most need to call. Click at the start of line 3 and type **LEFT** and a space, so it reads **LEFT JOIN orders o ON o.customer = c.name**.
    Only four rows. Elm Street Law is missing, because a plain JOIN drops customers with no orders.
15. **Run it.** Click **Run**.
    Run it.
16. **Keep only the quiet ones.** Five rows: Elm Street Law is back, with **null** (no orders). Now keep only customers with nothing since 1 September. Delete the semicolon at the end of the GROUP BY line, press Enter and type the code shown below.
    Elm Street Law is back, with null. Now keep only customers with no order since the first of September, or no order at all.
17. **Run the call list.** Click **Run**.
    Run the call list.

## Screenshots

[Start this module free](https://learn.ynteractive.com/modules/sql-quiet-customers)

- Previous in SQL: [SQL: Top Customers and Key Accounts with GROUP BY and HAVING](https://learn.ynteractive.com/content/sql-top-customers)

## More in SQL

- [SQL: Build a Monthly Revenue Report from an Orders Table](https://learn.ynteractive.com/content/sql-monthly-revenue-report): A beginner SQL walkthrough in the free DB Fiddle: type a small orders table, then filter it, total it and turn it into revenue by month with GROUP BY, typing every line…

[All 3 modules in SQL](https://learn.ynteractive.com/content/course/sql)

## Same business, other tools

Maple Dental shows up in these modules too, built with different tools.

- [Excel for the Web: Find Your Top Customers in a Sales Export](https://learn.ynteractive.com/content/excel-web-top-customers): A beginner Excel for the web walkthrough on real screens: clean a sales export with Remove Duplicates, total every customer with a PivotTable and sort the biggest to…
- [JavaScript: Turn Invoice Dates into Due-Date Reminders](https://learn.ynteractive.com/content/js-due-date-reminders): A beginner JavaScript walkthrough in the free JSFiddle: work out Net 30 due dates, count the days left and list every invoice as due or overdue, typing every line…
- [Python: Total a Sales Export by Customer in Google Colab](https://learn.ynteractive.com/content/python-sales-report): A beginner Python walkthrough in the free Google Colab: put six orders in a pandas table, total the quarter and rank customers by revenue, typing every line yourself.
- [Python: Combine Monthly Sales Exports into One Quarter](https://learn.ynteractive.com/content/python-combine-exports): A beginner Python walkthrough in the free Google Colab: label three monthly exports, stack them into one quarter with pandas concat and total by month and by customer…

## Free cheat sheet

Print it or save the PDF: the key steps and checks from this lesson on one page, free.

- [SQL Business Reports Cheat Sheet](https://learn.ynteractive.com/content/cheat-sheets/sql-business-reports): A free one-page SQL cheat sheet: SELECT, WHERE, SUM, GROUP BY, HAVING, ORDER BY, LIMIT and LEFT JOIN, with the three report queries from the course.

[All free printable cheat sheets](https://learn.ynteractive.com/content/cheat-sheets)

## Terms in this lesson

Plain-English definitions, each with an example from a free lesson.

[LEFT JOIN (SQL)](https://learn.ynteractive.com/content/glossary/left-join) · [SQL](https://learn.ynteractive.com/content/glossary/sql) · [GROUP BY (SQL)](https://learn.ynteractive.com/content/glossary/group-by)

[The full AI glossary](https://learn.ynteractive.com/content/glossary)

## Browse related tutorials

[SQL (3)](https://learn.ynteractive.com/content/course/sql) · [DB Fiddle tutorials (3)](https://learn.ynteractive.com/content/tool/db-fiddle)

Want AI working like this in your business? Robert Breen, the instructor behind this lesson, helps small and mid-sized teams put AI assistants, agents and automations to work. [Work with Robert on AI consulting](https://ynteractive.com/)