Module C Preface

A lot of the data that we interact with today is stored in databases. You can think of a database as a group of tables. These tables have rows and columns just like spreadsheets. Some examples of data that can be stored in databases are listed below.

• Student records, including grades, at a school

• Posts and friends in your favorite social network

• News stories on a newspaper’s website

• Your contacts list on your mobile phone

• All images that make up Google Maps

All these bits of information are stored in various kinds of databases. Some of these are stored in a relational database, which is a database that stores data points that are related to one another in some way. These databases are available as open source tools like Postgresql, MySQL and SQLite, as well as commercial databases such as Google BigQuery, Oracle, Microsoft SQL Server, or Amazon Aurora. Others are stored in proprietary systems like Google’s BigTable or Facebook’s Haystack Object Store.

While the mechanism and content of the database may vary, there is a common language used to extract data: this language is called Structured Query Language (SQL, pronounced “sequel”). This module will teach you how you can use SQL to analyze data in a database.

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