Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 8: Being Normal: Normalization and Other Basic Design Issues
Figure 8-2
At this point, we meet our criteria for first normal form. We have no repeating groups of data, and all
columns are atomic. We do have issues with data having to be repeated within a column (because it’s the
same for all rows for that primary key), but we’ll deal with that shortly.
The Second Normal Form
222
Order No
(PK)
100
100
100
100
101
102
102
102
103
103
103
Line Item
(PK)
1
2
3
4
1
1
2
3
1
2
3
Rather than create another column as we did here, we also could have taken the
approach of making PartNo part of our primary key. The fallout from this would
have been that we could not have had the same part number appear twice in the
same order. We’ll briefly discuss keys based on more than one column — or composite
keys — in our next chapter.
The next phase in normalization is to go to the second normal form (2NF). Second normal form further
reduces the incidence of repeated data (not necessarily groups).
Second normal form has two rules to it:
Order Date Customer No Part No Description Qty Unit Price Total Price Wt.
1/1/1999
1/1/1999
1/1/1999
1/1/1999
1/1/1999
1/1/1999
1/1/1999
1/1/1999
1/2/1999
1/2/1999
1/2/1999
54545
54545
54545
54545
12000
66651
66651
66651
54545
54545
54545
1A4536
0R2400
0R2403
4I5436
3X9567
8G9200
8G5437
3H6250
8G9200
2P5523
3X9567
❑ The table must meet the rules for first normal form. (Normalization is a building block kind of
process — you can’t stack the third block on if you don’t have the first two there already.)
❑ Each column must depend on the whole key.
Flange
Injector
Injector
Head
Pump
Fan
Fan
Control
Fan
Housing
Pump
Our example has a problem — actually, it has a couple of them — in this area. Let’s look at the first normal
form version of our Orders table again (Figure 8-2) — is every column dependent on the whole
key? Are there any that need only part of the key?
The answers are no and yes respectively. There are two columns that only depend only on the OrderNo
column — not the LineItem column. The columns in question are OrderDate and CustomerNo; both are
the same for the entire order regardless of how many line items there are. Dealing with these requires
that we introduce yet another table. At this point, we run across the concept of a header vs. a detail table
for the first time.
5
4
4
1
1
7
1
1
40
1
1
15
27
29
750
62.50
12
15
32
12
165
42
75
108
116
750
62.50
84
15
32
480
165
42
6
.5
.5
3
5
3
3
5
3
1
5