Vol. I · A Postgres HandbookTwelve chapters · · 756 queries

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

EasyBasic SELECT

List all unique countries from customers

SQL

SELECT DISTINCT country
FROM customers
WHERE country IS NOT NULL
ORDER BY country;

Tested against PostgreSQL 16

Note

“Always filter out NULLs when getting distinct values for cleaner results.