Databases and SQL are essential skills for data professionals, as they enable them to store, retrieve, and manipulate data efficiently. However, learning databases and SQL is not just about writing queries, but also understanding the underlying concepts, models, and design principles. Fortunately, there are many free online courses from top universities that can help you learn databases and SQL in depth. In this article, we will introduce you to five of them and highlight their main features.

Learn SQL and NoSQL Systems with Cornell University

Cornell University offers a comprehensive course on Introduction to Databases, which covers both SQL and NoSQL systems. The course is taught by Professor Immanuel Trummer, who is an expert in database systems and data science. The course covers the following topics:

SQL: You will learn the basics of SQL, such as creating tables, inserting data, querying data, joining tables, aggregating data, and modifying data. You will also learn advanced SQL features, such as subqueries, views, triggers, and stored procedures.
NoSQL: You will learn about the different types of NoSQL systems, such as key-value stores, document stores, column stores, and graph databases. You will also learn how to use them for various applications, such as web development, social networks, and analytics.
NewSQL: You will learn about the new generation of SQL systems, which combine the scalability and performance of NoSQL systems with the consistency and reliability of SQL systems. You will also learn how to use them for large-scale data processing and transaction processing.
Data Storage and Indexing: You will learn how databases store and index data on disk and in memory, and how to optimize them for different workloads and queries.

Relational Data Processing: You will learn how databases execute relational queries, such as joins, selections, projections, and aggregations, and how to optimize them using query plans, query optimization, and query execution.
Transaction Processing: You will learn how databases ensure the correctness and consistency of data updates, and how to handle concurrency and recovery issues using transaction models, isolation levels, locking protocols, and logging mechanisms.
Database Design: You will learn how to design databases that are efficient, reliable, and easy to maintain, and how to use data models, schemas, normalization, and denormalization techniques.
Distributed Data Processing: You will learn how to use databases in distributed environments, such as cloud computing and big data, and how to deal with challenges such as replication, partitioning, sharding, and consistency.
Beyond Relational Data: You will learn how to use databases for non-relational data, such as text, images, videos, and geospatial data, and how to use techniques such as full-text search, multimedia processing, and spatial indexing.

The course is self-paced and consists of video lectures, quizzes, assignments, and projects. You can audit the course for free or pay a fee to get a certificate.

Learn Relational Databases with Harvard University

Harvard University offers a course on Introduction to Databases with SQL, which is part of the CS50 series of courses. The course is taught by Professor David J. Malan, who is a renowned computer science educator and researcher. The course covers the following topics:

Querying: You will learn how to use SQL to query data from relational databases, such as SQLite, MySQL, and PostgreSQL. You will also learn how to use functions, operators, expressions, and clauses to filter, sort, group, and aggregate data.
Relating: You will learn how to use SQL to relate data from multiple tables, using primary keys, foreign keys, and constraints. You will also learn how to use joins, subqueries, and unions to combine data from different sources.
Designing: You will learn how to use SQL to design databases that are logical, consistent, and normalized. You will also learn how to use entity-relationship diagrams, functional dependencies, and normal forms to model data and avoid anomalies.
Writing: You will learn how to use SQL to write data to relational databases, using commands such as INSERT, UPDATE, DELETE, and ALTER. You will also learn how to use transactions, triggers, and indexes to ensure data integrity and performance.
Viewing: You will learn how to use SQL to view data from relational databases, using commands such as CREATE VIEW, DROP VIEW, and ALTER VIEW. You will also learn how to use views to simplify queries, hide details, and enforce security.
Optimizing: You will learn how to use SQL to optimize queries and databases, using tools such as EXPLAIN, ANALYZE, and VACUUM. You will also learn how to use query optimization techniques, such as query rewriting, query decomposition, and query evaluation.
Scaling: You will learn how to use SQL to scale databases and handle large amounts of data, using concepts such as sharding, replication, and caching. You will also learn how to use distributed databases, such as MongoDB, Cassandra, and HBase, to achieve scalability and availability.

The course is self-paced and consists of video lectures, quizzes, problem sets, and projects. You can audit the course for free or pay a fee to get a certificate.

Learn Advanced Topics in SQL with Stanford University

Stanford University offers a series of courses on Databases, which cover various aspects of database systems and SQL. The series is taught by Professor Jennifer Widom, who is a world-renowned database researcher and educator. The series consists of five courses, which are:

Databases: Relational Databases and SQL: This course covers the basics of relational databases and SQL, such as creating tables, querying data, joining tables, aggregating data, and modifying data. This course is recommended as the first course in the series, as it provides the foundation for the subsequent courses.
Databases: Advanced Topics in SQL: This course covers advanced topics in SQL, such as query performance, transaction and concurrency control, database constraints, triggers, and creating and updating database views. This course is useful for those who want to learn how to use SQL more effectively and efficiently.
Databases: OLAP and Recursion: This course covers topics related to online analytical processing (OLAP) and recursion in SQL, such as OLAP cubes, star schema, OLAP features, and SQL queries with recursive relations. This course is useful for those who want to learn how to use SQL for analytical purposes and complex queries.
Databases: Modeling and Theory: This course covers topics related to database modeling and theory, such as relation algebra, normal forms, recursive relations, and UML. This course is useful for those who want to learn how to design databases that are logical, consistent, and normalized.
Databases: Semistructured Data: This course covers topics related to semistructured data, such as JSON and XML, and how to use them with SQL. This course also covers the basics of XPath and XSLT, which are languages for querying and transforming XML data. This course is useful for those who want to learn how to use SQL for non-relational data.

The courses are self-paced and consist of video lectures, quizzes, exercises, and exams. You can audit the courses for free or pay a fee to get a certificate.

Learn Database Systems with Carnegie Mellon University

Carnegie Mellon University offers two courses on database systems, which cover the fundamentals and the advanced topics of database systems. The courses are taught by Professor Andy Pavlo, who is a leading expert in database systems and data engineering. The courses are:

Intro to Database Systems: This course covers the fundamentals of database systems, such as data storage and compression, memory and disk I/O management, data structures (hash tables, B+ trees), and query processing and optimization. This course also covers the basics of SQL and relational algebra, and how to use them to manipulate data. This course is useful for those who want to learn how databases work under the hood, and how to use them efficiently.
Advanced Database Systems: This course covers the advanced topics of database systems, such as transaction processing and recovery, concurrency control and isolation, distributed and parallel databases, and database security and privacy. This course also covers the modern trends and challenges of database systems, such as cloud computing, big data, and machine learning. This course is useful for those who want to learn how to build and manage complex and scalable database systems, and how to use them for data-intensive applications.

The courses are self-paced and consist of video lectures, quizzes, assignments, and projects. You can audit the courses for free or pay a fee to get a certificate.

Conclusion

Databases and SQL are vital skills for data professionals, as they enable them to store, retrieve, and manipulate data efficiently. However, learning databases and SQL is not just about writing queries, but also understanding the underlying concepts, models, and design principles. Fortunately, there are many free online courses from top universities that can help you learn databases and SQL in depth. We have introduced you to five of them and highlighted their main features. Choose the course that suits your learning goals and level up your data skills!