Database Reference
In-Depth Information
OrderLine
OrderNum
PartNum
Description
NumOrdered
QuotedPrice
21608
AT94
Iron
11
$21.95
21610
DR93
Gas Range
1
$495.00
21610
DW11
Washer
1
$399.99
21613
KL62
Dryer
4
$329.95
21614
KT03
Dishwasher
2
$595.00
21617
BV06
Home Gym
2
$794.95
21617
CD52
Microwave Oven
4
$150.00
273
21619
DR93
Gas Range
1
$495.00
21623
KV29
Treadmill
2
$1,290.00
FIGURE 8-12
Including part descriptions in the OrderLine table, which creates a first normal form table
The OrderLine table in Figure 8-12 is in first normal form because there are no repeating groups. Because
a part description depends only on the part number, which is just a portion of the primary key for the table,
the OrderLine table is not in second normal form and, consequently, is not in third normal form either. As a
result, the table has redundancy and anomaly problems that are inherent in tables that are not in third nor-
mal form. However, users processing order lines no longer need to join the OrderLine and Part tables to
obtain part descriptions, thus improving performance.
Large databases with thousands of users often suffer periodic performance problems as users change their
transaction mix. In these cases, the DBA must tune the databases to provide improved performance to all
users.
