- Use primary and foreign keys to create the relations in a relational database.
- Use
INNER JOINandLEFT JOINto retrieve relevant data for members of one table in other tables. - Use joins to create one-to-many and many-to-many relationships between tables.
- Primary Key: a number that uniquely identifies one record in a table.
- Foreign Key: a column or group of columns that connects one table to another.
- Join: a query that returns related records from multiple tables in a single record.
- One-to-Many: a type of relationship between tables where one record in table A is connected to multiple records in table B. e.g. One person ordering multiple drinks at a bar.
- Many-to-Many: a type of relationship between tables where multiple records in table A are connected to multiple records in table B. e.g. Students have many classes and classes have many students.
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 one-to-many and many-to-many relationships
- How a join table is used
- 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.
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