​Learn the most important parts of the SQL language so you can create tables with constraints, use relationships, and write powerful join queries.

Learn how to use SQL aggregate functions, including COUNT, SUM, and AVG, to do calculations on groups of data.
Add constraints — like NOT NULL, UNIQUE, FOREIGN KEY, and PRIMARY KEY — to your tables to increase data integrity.
Apply normalization rules to create tables without duplicate data and build the appropriate relationships.
Explore writing a single query to pull data from multiple tables and using aliases to create succinct queries.
Dive deeper as you learn how to write queries within queries.