User guide

Tasks Involved in Developing Your Data Base
Developing the Data Base
058058 Tandem Computers Incorporated 2–3
Key Fields A key field is a field whose value an application can use to identify a specific record
occurrence. Sometimes more than one field is needed to identify a record. When two
or more contiguous fields are used to identify a record occurrence, the combined fields
are called composite key fields. The two categories of key fields are primary key fields
and alternate key fields.
A primary key field is a field whose value an application uses to uniquely identify a
particular record occurrence. Only one primary key field can exist for a record. A
likely primary key field for parts is partnum because this field uniquely identifies each
record occurrence of parts. Odetail requires a composite key composed of both
ordernum and partnum because the same part number could occur in many orders and
the same order number could contain many part numbers.
An alternate key field is a field whose value an application uses to identify all record
occurrences with a certain property. A record can have more than one alternate key.
When an alternate key is specified for a record, an alternate search path exists that can
be used to retrieve data. The presence of alternate keys affects any application that
uses the data base. Refer to Section 5 for more information about alternate key fields.
Tasks Involved in
Developing Your
Data Base
The following discussion describes the tasks involved in developing your data base.
The tasks are:
Normalizing the data.
Describing the data base.
Creating the physical files that store the data.
Loading the data.