Joins

In this section, we will only discuss inner joins, and equijoins, as in general, they are the most useful. For more information, try the SQL links at the bottom of the page.

Good database design suggests that each table lists data only about a single entity, and detailed information can be obtained in a relational database, by using additional tables, and by using a join.

First, take a look at these example tables:

AntiqueOwners

OwnerID	OwnerLastName	OwnerFirstName
01	Jones	Bill
02	Smith	Bob
15	Lawson	Patricia
21	Akins	Jane
50	Fowler	Sam

Orders

OwnerID	ItemDesired
02	Table
02	Desk
21	Chair
15	Mirror

Antiques

SellerID	BuyerID	Item
01	50	Bed
02	15	Table
15	02	Chair
21	50	Mirror
50	01	Desk
01	21	Cabinet
02	21	Coffee Table
15	50	Chair
01	15	Jewelry Box
02	21	Pottery
21	02	Bookcase
50	01	Plant Stand