PostgreSQL, Second Edition

Multi-Table Joins

So far, all the queries that you've seen involve a single table. Most databases contain multiple tables and there are relationships between these tables. This sample database has an example:

movies=# \d rentals

            Table "rentals"
  Attribute  |     Type     | Modifier
-------------+--------------+----------
 tape_id     | character(8) | not null
 rental_date | date         | not null
 customer_id | integer      | not null

Here's a description of the rentals table from earlier in this chapter:

“When a customer comes in to rent a tape, we will add a row to the rentals table to record the transaction. There are three pieces of information that we need to record for each rental: the tape_id, the customer_id, and the date that the rental occurred. Notice that ...