2.11: Join

In this lesson, you'll learn how to query data from multiple tables. This short video will introduce the concept of an "inner join," which is the type of join you'll be using below. You can also read more about joining tables in PostgreSQL by clicking here.

Start by copying and pasting this code into a query in pgAdmin. This will populate the table you created in the previous lesson.

INSERT INTO Purchases (
    VALUES (1, 1, 1, 5),
    (2, 1, 2, 5),
    (3, 2, 4, 3)
);

This is what the resulting table should look like:

Purchase table after insert

Now, write a query that will return a table containing the customer's first names that have a PurchaseID. You'll have to use an "INNER JOIN" to accomplish this. Remember that you are also working with multiple tables, so consider which tables have the data you are querying for. Finally, think about what columns these tables have in common.

The resulting table output from your query should look like this:

Table output inner join

To see the solution for this challenge, click on 2.12 Solutions. For additional challenges, please continue to Part Four.