Sql And Postgresql- The Complete Developer-s Guide -

CREATE TABLE products ( id SERIAL PRIMARY KEY, name TEXT NOT NULL, price DECIMAL(10,2) CHECK (price > 0), metadata JSONB );

You cannot use a column alias in the WHERE clause because WHERE executes before SELECT . You can use it in ORDER BY . SQL and PostgreSQL- The Complete Developer-s Guide

SELECT email FROM users u WHERE EXISTS (SELECT 1 FROM orders o WHERE o.user_id = u.id); CREATE TABLE products ( id SERIAL PRIMARY KEY,