Select All Customers

Problem

Schema: Customer(id INT, name VARCHAR, country VARCHAR). Return every column of every row in Customer, ordered by id ascending.

Constraints

• id is unique.
• name and country are NOT NULL.

Approach — Core Patterns

This is a Core Patterns problem. The idea: pick the data structure best matched to the constraints and solve it in one clean pass. Work through the reference code below line by line, then re-derive it yourself in the editor — that's how the pattern sticks.

Complexity: see the walkthrough below.

Solution code

SQL

SELECT id, name, country
FROM Customer
ORDER BY id;

Practice it

Reading a solution isn't the same as being able to write it under pressure. Open this problem in the in-browser editor, hide the solution, and solve it from scratch — your code runs against real test cases instantly.