About MockDojo

What you can practice

Public PostgreSQL exercises let you inspect datasets, write queries, compare actual output and debug errors in your browser. Browse SQL practice without an account, or use the SQL guides to understand the reasoning behind a query. Topics include filtering, joins, aggregation, missing values and window functions.

Account features include a SQL course, training plans, progress history, resume feedback and AI mock interviews. Some features depend on separate provider configuration or paid access and show their availability in the product.

How to interpret results

Browser query results are learning checks against authored datasets. They are not secure certifications. Engagement XP measures participation; demonstrated mastery requires the appropriate verified evidence. Self-reported interview outcomes and AI estimates remain labeled separately. AI feedback may be wrong and does not predict whether an employer will hire you.

How the guides are prepared

MockDojo publishes original explanations and small, reproducible PostgreSQL examples. The aggregation and window-function guides include complete input data and expected output, checked against PostgreSQL in the project test suite. Examples are deliberately small enough to reason about row by row. A passing example does not imply every possible database or business rule has been tested.

If an explanation is unclear or a dataset seems incorrect, send a correction with the public page URL and a small, non-sensitive reproduction.

Practice honestly

Use MockDojo to prepare before interviews and strengthen your own understanding. Do not use it to secretly answer a live assessment, impersonate another candidate or violate an employer’s rules. MockDojo is an education product, not a job board, recruiting agency or credential issuer.