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N020-M4 Tier 2 · Core SQL · medium ecommerce · Brightlane

Return each premium product paired with every category, returning the product name, price, and category name

Part of CROSS JOIN in SQL

The problem

Brightlane's pricing team wants to analyse how premium products — those with a list price above $500 — could be positioned across every available category.

Write a query to return each premium product paired with every category, returning the product name, price, and category name.

Assumptions:

  • The products table contains every product in the catalogue.
  • The categories table contains every defined category.
  • The premium condition narrows the result to products with price > 500 before they are paired with categories.

Output:

  • One row per premium-product × category combination, with columns product_name, price, and category_name.
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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Solution query
SELECT
  p.name AS product_name,
  p.price,
  c.name AS category_name
FROM
  products p
  CROSS JOIN categories c
WHERE
  p.price > 500

The shape

WHERE p.price > 500 narrows products to the premium cohort, and CROSS JOIN categories c expands each premium product across every category — including the category it currently sits in. The output carries three columns: the product name, its price (for the pricing team to see directly), and the candidate category.

Clause by clause

  • FROM products p CROSS JOIN categories c is the unconditional pairing. Every row in products combines with every row in categories.
  • WHERE p.price > 500 filters the left side to products whose list price exceeds $500. The comparison is strict — a product at exactly 500 does not pass. Premium, by the pricing team's working definition, sits above that threshold.
  • p.name AS product_name and p.price read two columns from the products side. The price column doesn't need an alias because it's already named appropriately; PostgreSQL will return it as price.
  • c.name AS category_name reads the candidate category from the right side. The alias c disambiguates this name column from the product's name column on the left.

Why include price in the output

The team is analysing positioning. Seeing each pairing alongside its price keeps the analysis self-contained — the reader doesn't have to cross-reference back to the product table to know which premium tier a given pairing represents. A $1,199 product positioned in Home Goods reads differently from a $549 product positioned in the same category. Carrying the price through makes that visible in the result without a second query.

You practiced CROSS JOIN against a price-filtered cohort. The premium-positioning use case is the everyday version of "hypothetical placement," where the cross-product is the answer because no actual relationship has been decided yet.

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