Intro to Table Relations in SQL: Software Engineering Full time 13 Phase 3 Hybrid

Learning Goals

Use primary and foreign keys to create the relations in a relational database.
Use INNER JOIN and LEFT JOIN to 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.

Key Vocab

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.

Introduction

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.