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Join Types

When you build a system based on normalized table structures, you must join the tables back together to see the data in a useable format. For example, if you have separated customers, orders, and order details, you will need to join these tables in a query to see the name of the customer who placed an order for a particular item. Several types of joins are available. They include inner joins, outer joins, full joins, and self-joins. The sections that follow cover each of these join types.

Inner Joins

An inner join is the most common type of join. When you use an inner join, only rows on the one side of the relationship that have matching rows on the many side of the relationship are included in the output. Here's an example:


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