SQL is a skill you acquire by running queries against data and being wrong a lot. Reading a tutorial produces recognition ("yes, that is a LEFT JOIN"); typing sixty queries produces recall, and recall is what an interview or a production incident actually tests. The problem for beginners is that running queries traditionally starts with installing a database, and "install PostgreSQL" is where a lot of SQL journeys quietly end.
Browser-based database terminals remove that step. Below is a practice path through three of them, each free and signup-free, and each covering a different layer of the skill: the SQL language itself, the psql client you will meet at work, and the document-database alternative for contrast.
Layer 1: the SQL language
The SQL Terminal Simulator is a guided path of 13 lessons against a small commerce dataset: customers, orders, order_items, products. It starts at SELECT and ends at common table expressions and window functions.
The progression, with one example of each rung, all runnable in the simulator:
