Knowing at least the basics of writing SQL is a useful programming skill. The majority of databases you'll work with as a developer will have more than one table, and those tables will be connected together in various ways to form table relationships.

In this section we'll cover:

• The structure of a relational database as tables
• Primary key and foreign keys
• How to associate data tables using a foreign key column
• How to model a "many-to-many" object association
• How a join table is used
• Distinguishing the different types of relationships between data in a database
• Different types of joins

Over the next several lessons we'll discuss having multiple tables in a database, how to define relationships between different tables, and explain the different types of table relationships that can exist.