SQL Roadmap

Learn SQL step by step — 34 free lessons with spaced repetition and active recall on RetainHQ, so what you study actually sticks.

Lessons

• Aggregate Functions
• CASE Expressions
• Constraints & defaults
• Correlated Subqueries
• CTEs (WITH)
• DISTINCT
• FULL OUTER & CROSS JOIN
• GROUP BY
• HAVING vs WHERE
• How Databases Use Indexes
• Indexes — what & when
• INNER JOIN
• INSERT & Returning
• ON vs USING & Join Keys
• Primary, foreign & unique keys
• LEAD & LAG
• LEFT / RIGHT JOIN
• Multi-Column Grouping
• Normalization (1NF–3NF)
• Data Types & NULL Handling
• ORDER BY, LIMIT & OFFSET
• OVER & PARTITION BY
• Common Query Pitfalls & Anti-patterns
• Reading EXPLAIN ANALYZE
• ROW_NUMBER / RANK / DENSE_RANK
• Recursive CTEs
• SELECT, FROM & Columns
• Self Join
• Scalar & IN Subqueries
• Transactions (BEGIN, COMMIT, ROLLBACK)
• UPDATE, DELETE & Returning
• UPSERT (ON CONFLICT)
• WHERE & Operators
• Running totals & moving averages