User guide

Tasks Involved in Developing Your Data Base
Developing the Data Base
2–4 058058 Tandem Computers Incorporated
Normalizing the Data ENFORM (and most other applications that access the data base) will retrieve data
most efficiently when record occurrences do not contain repeating groups. Remember,
a repeating group is a field that stores more than one value.
Use the process of normalization to remove the repeating groups from your data.
Consider Figure 2-3 which shows the record occurrences of oldorder. In oldorder both
partnum and quantity are repeating groups.
Figure 2-3. Record Occurrences With Unnormalized Data
partnum
244
2001
2403
4103
244
5103
6301
6402
Oldorder Record Occurrences
ordate deldate
011078
012378
quantity custnum
• • • • • • • • • • • •• • •
ordernum
• • •
041078
061578
1
2
2
2
1
2
1
10
1234
7777
21
25
The process of normalization removes the repeating groups. Four levels of
normalization exist. This guide discusses only the first level of normalization: first
normal form. First normal form exists when the following condition is satisfied:
For every field in a record occurrence there exists precisely one value, never a group of
values.
Figure 2-4 shows the record occurrences that result when oldorder is normalized in first
normal form. The new record is named neworder.