Customers with Missing City — IS NULL in SQL

The problem

Brightlane's data quality team is auditing incomplete customer profiles ahead of a CRM migration to a new system.

Write a query to return the name and email of every customer whose city has not been recorded.

Assumptions:

The customers table contains every customer Brightlane has on file.
Some customers have a recorded city value; others have city set to NULL.
A missing city is stored as NULL, not as an empty string.

Output:

One row per customer with no city on file, with columns name and email.

Schema · ecommerce 5 tables

categories

id integer

name text

parent_id? integer

products

id integer

name text

category_id integer

price numeric

stock_qty integer

attributes? jsonb

order_items

id integer

order_id integer

product_id integer

quantity integer

unit_price numeric

customers

id integer

name text

email text

city? text

country text

created_at timestamptz

is_active boolean

orders

id integer

customer_id integer

ordered_at timestamptz

status text

total_amount numeric

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Worked solution Try it yourself first

Solution query

SELECT
  name,
  email
FROM
  customers
WHERE
  city IS NULL

The shape

IS NULL is the only operator that detects a missing value. The CRM audit wants every customer with no city on file, so the WHERE clause asks that question directly.

Clause by clause

SELECT name, email returns the two columns the audit needs — the customer's name and how to reach them. city itself stays out of the output; it's NULL for every row in the result.
FROM customers reads the customer records. The prompt's assumption that this table contains every customer Brightlane has on file is what makes the result complete.
WHERE city IS NULL keeps only rows whose city is absent. IS NULL returns true for those rows and false for everyone with a city recorded.

The trap

WHERE city = NULL looks like it should work and returns zero rows every time. Comparing anything to NULL with = produces unknown, never true, and WHERE only keeps rows whose condition is clearly true. The query runs without error, the result comes back empty, and the audit silently misses every account it was supposed to find. Use IS NULL whenever the test is for absence.

You practiced testing for the absence of a value with IS NULL. The = operator can't match NULL — IS NULL is the only correct test for missing data.

Return the name and email of every customer whose city has not been recorded

The shape

Clause by clause

The trap

Reading explains SQL. Writing it, over and over with instant feedback, is what makes you fluent.