Inside the databaseAn interactive learning studio for relational databases

How this studio works

Press Run query and the query plays through the database on its own. Pause, resume or replay it from the progress strip, and select any part of the scene to explain it in the inspector.

Kinds of lesson

Query flow is an animated, simplified model. The hands-on labs, Practice, Visualize and Challenges run real PostgreSQL 18 inside this tab (PGlite): nothing is sent anywhere. The HNSW vector search lesson is an interactive simulation of pgvector's index on a fixed demo dataset.

Query flow's SQL

The animation follows a SELECT, INSERT, UPDATE or DELETE on the users table (use the buttons above the editor); anything else can run in the SQL Lab:

SELECT … / UPDATE … / DELETE … WHERE id = <number>, or INSERT INTO users (name, email) VALUES (…)

The users table holds ids 1-56. Try an id outside that range to see an empty result, or INSERT an id that exists to see a duplicate-key error.

About the model

It is a simplified model of PostgreSQL. Real databases add steps (locks, visibility checks, statistics, the OS cache) and the details differ by engine and configuration.

Plan visualizer

See the plan PostgreSQL really picks. Earlier statements run first; the last one is explained.

Starting PostgreSQL in your browser…

SELECT c.name, count(DISTINCT o.id) AS orders, sum(oi.quantity * oi.unit_price) AS spent
FROM customers c
JOIN orders o ON o.customer_id = c.id
JOIN order_items oi ON oi.order_id = o.id
GROUP BY c.name
ORDER BY spent DESC;

ANALYZE executes the statement and reports real row counts and times. For INSERT, UPDATE or DELETE that means the change really happens.

Try a sample

Press Explain to draw the plan. Rows flow upward: each node feeds the one above it.