Harvard CS50 · Harvard University
CS50's Introduction to Databases with SQL
Harvard's SQL course combines querying, relational database design, data modification, and performance concepts with problem sets.
Beginner10+ hoursCertificate
SQL courses and tutorials
Compare SQL courses and interactive lessons for querying, joins, grouping, and database reasoning, with guidance on dialects and meaningful practice data.
3 learning resources in this collection
About SQL
SQL expresses questions and changes against structured data. A useful foundation includes tables, keys, filtering, joins, grouping, and the meaning of missing values. The central skill is translating a question into a result you can verify.
Choose a useful starting point
Use SQLBolt for focused interactive practice, or choose a longer course for broader database work. CS50 SQL adds a university-style route. Check which database dialect is used and avoid treating a query that runs as proof that its joins or totals are correct.
Build on the lessons
Create a tiny dataset where you can predict the answer by hand. Test a duplicate, a missing relationship, and a null value. Explain why the query returns each row.