Job Ready SQL

Lesson 1Exploring Relational Databases and SQL

SQL is used to access data. Before jumping into SQL and how it is used, it is important to step back and consider how information that you will access has been stored. In this chapter, you'll dive into the topic of data and databases to set the foundation for then accessing the information. You will get a high‐level look at databases in general and at relational databases specifically.

Learning Objectives

By the end of this lesson, you will be able to:

• Describe what a relational database is, how it works, and how it differs from a database management system (DBMS)
• Define database tables, relations, columns, attributes, rows, records, tuples, and data types
• Identify the ACID properties
• Know about entity integrity and uniqueness using keys
• Discuss database backup strategies

SAVING DATA

To be useful, software systems must remember. If your character started at the beginning (level 0) every time you fired up a video game, or your online banking app reset your balance to $0 when you logged off, or your phone forgot your contacts when it rebooted, you wouldn't use them. To remember, applications must save data in a way that allows ready access to that data when needed.

There are a few options for saving data.

• Write text or bytes directly into a file
• Store data in a relational database
• Store data in a nonrelational database

The first option of writing directly into a file can be cumbersome. In this case, the file typically ...