Data used for analysis is rarely stored in one monolithic table. For reasons of organization and efficiency, information is typically spread across several related tables. Consequently, a common task is to bring data together from these different tables to get a complete picture.
This chapter focuses on techniques for combining data from multiple tables using SQL. We will start by examining the structural elements that link tables: primary and foreign keys. You will then learn about SQL JOIN
operations, concentrating on the INNER JOIN
clause to merge rows based on matching criteria. We'll cover joining two tables, extending the concept to combine multiple tables, and using table aliases to simplify query syntax. Upon completing this chapter, you will understand how to construct queries that integrate data from various related tables for comprehensive analysis.
5.1 Why Combine Data?
5.2 Understanding Primary and Foreign Keys
5.3 Introduction to SQL JOINs
5.4 Using INNER JOIN
5.5 Joining Multiple Tables
5.6 Using Aliases for Tables
5.7 Hands-on Practical: Writing INNER JOIN Queries
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