CS50's Introduction to Databases with SQL

CS50's Introduction to Databases with SQL teaches relational databases from the ground up. You learn to create, read, update and delete data; to model real-world entities and relationships with tables, types, triggers and constraints; to normalize data to remove redundancy; to join tables with primary and foreign keys; to automate queries with views and speed them up with indexes; and to connect SQL to languages such as Python and Java. The course starts with SQLite for portability and ends with introductions to PostgreSQL and MySQL for scalability. Its seven weeks of material each pair a lecture with a problem set based on real-world datasets, and the course closes with a final project.

It is free to take through Harvard's OpenCourseWare, and a free edX account lets you submit work for feedback. Scoring at least 70% on every problem and the final project earns a free CS50 Certificate; a verified certificate is available through edX for a fee. Harvard lists the difficulty as introductory and the time commitment as 6 to 12 hours per week, and says the course can be taken before, during or after CS50x.