In this section, we will only discuss inner joins, and equijoins, as in general, they are the most useful. For more information, on Joins you may wish to acquire a reference manual which will discuss the other options in more detail.
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
