| 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 |
|
