Customers who never ordered

Easy

Question

An online shop wants to send a discount code to every customer who has never placed an order.

Some orders were made at checkout as a guest. For a guest order the column customer_id is NULL.

Return id and name of every customer with no order. The order of the rows does not matter.

join
anti join
left join
not exists
null

Read first: Lesson 44, SQL joins: inner, left, anti-join and self-join

Tables

2 tables

These are the example rows. Run uses only these rows. Submit also tests your query on a second set of rows that you cannot see.

customers3 columns · 7 rowsnot run yet

CREATE TABLE customers (id INTEGER PRIMARY KEY, name TEXT NOT NULL, city TEXT NOT NULL);

Example rows of the customers table
id	name	city
1	Aarav	Mumbai
2	Bhavna	Pune
3	Chirag	Delhi
4	Divya	Mumbai
5	Eshan	Chennai
6	Farah	Pune
7	Gautam	Delhi

orders4 columns · 7 rowsnot run yet

CREATE TABLE orders (id INTEGER PRIMARY KEY, customer_id INTEGER REFERENCES customers(id), amount INTEGER NOT NULL, ordered_at TEXT NOT NULL);

Example rows of the orders table
id	customer_id	amount	ordered_at
1	1	500	2026-02-01
2	1	250	2026-02-03
3	NULL	900	2026-02-04
4	3	300	2026-02-07
5	NULL	150	2026-02-09
6	5	450	2026-02-10
7	3	700	2026-02-12

About this SQL

This works the same in Postgres and MySQL. NULL is not equal to anything, not even to another NULL, so use IS NULL and IS NOT NULL. `x NOT IN (list)` is never true when the list contains a NULL, in every database.

SQLite

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Result

Run shows what your query gives on the example rows.Submit checks it on the example rows and on a hidden set of rows.

SQL · ready