Databases

Where data is kept, and the language used to ask it questions.

The SQL course comes first because every relational database speaks SQL. Courses on single database systems (PostgreSQL, MySQL, SQL Server, Oracle, and stores that are not relational, such as MongoDB and Redis) will sit beside it and link back to it instead of repeating it.

Course	What it covers
SQL, from beginner to expert	Standard SQL, tested on PostgreSQL and SQLite: queries, joins, grouping, window functions, CTEs, changing data, design, performance, and interview practice