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Oracle SQL: A Beginner’s Tutorial by Djoni Darmawikarta

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Chapter 5

Joins

A real-world database typically stores data in dozens or even hundreds of tables. In these multi-table databases, a table often relates to one or some other tables. In this environment, you should be able to relate rows from two or more tables by using the JOIN clause. This chapter shows you how.

Primary Keys and Foreign Keys

In Chapter 1, “Storing and Maintaining Data” you learned about primary keys. A primary key is a column, or a set of columns, which uniquely identifies every row in a table. A foreign key is a column, or a set of columns, which is used to relate to the primary key of another table. The process of using the foreign key/primary key to relate rows from two tables is called joining.

While a primary key must be ...

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