Active US Customers with Known City

The problem

Brightlane's email marketing team is running a location-targeted campaign and needs to reach only deliverable, active accounts.

Write a query to return the name and email of every active US customer who has a city on file.

Assumptions:

US customers are identified by country = 'US'.
Active customers are identified by is_active = true.
Some rows have a recorded city value; others have city set to NULL. A customer with city set to NULL is considered to have no deliverable address.

Output:

One row per qualifying customer, 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
  country = 'US'
  AND is_active = TRUE
  AND city IS NOT NULL

The shape

Three requirements joined by AND — country, active flag, and a non-null city all have to hold on the same row before it lands in the deliverable audience.

Clause by clause

SELECT name, email returns the two columns the email campaign needs.
FROM customers reads the customer table; the filter narrows from there.
WHERE country = 'US' AND is_active = true AND city IS NOT NULL chains three conditions. country = 'US' keeps US rows. is_active = true keeps active rows. city IS NOT NULL keeps rows where the city is on file. Every AND raises the bar — a row drops out the moment any single condition fails, regardless of whether the others passed.

Why `IS NOT NULL` and not `city <> ''`

A missing city is stored as NULL, not as an empty string. city <> '' compares against the empty string, and against NULL the comparison returns unknown — which WHERE drops. The NULL-city rows would slip through the filter, and the campaign would attempt delivery to an empty address. IS NOT NULL is the only operator that directly tests for the presence of a value, and it always returns true or false.

You practiced chaining three conditions with AND. The pattern scales without ceremony — each new requirement is one more condition joined by AND, and the row must satisfy every one to pass.

Return the name and email of every active US customer who has a city on file

The shape

Clause by clause

Why `IS NOT NULL` and not `city <> ''`

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

The shape

Clause by clause

Why IS NOT NULL and not city <> ''

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

Why `IS NOT NULL` and not `city <> ''`