INTRODUCTION
This section
introduces the structure of an xBASE database. Once you are familiar with the
database structure, you are guided though the creation of an actual database
that is used in activities contained in the following sections of this book.
THE DATABASE
STRUCTURE
The following
illustration is what you see when the structure of a database is listed on your
screen.
Field Field Name Type Width Dec
1 FNAME Character 15
2 LNAME Character 15
3 DATA Date 8
4 RATE Numeric 7 2
5 ABSENT Logical 1
6 COMMENTS Memo 10
Notice that the
database has six fields of varying types. Fields 1 and 2 are Character type, 3
is a Date, 4 is Numeric, 5 is Logical, and 6 is a Memo field. The database
files have the extension DBF.
The database
might contain information similar to that shown in the following table.
Record FÍME LNAME DATE RATE ABSENT COMMENTS
1 John Smith 10/12/42 12.50 .F. (Memo)
2 Alice Garica 02/21/68 9.60 .F. (Memo)
3 George Wong 06/05/72 7.75 .F. (Memo)
This table show
the first three records (001 through 003). Notice that the appreance of the
information matches the designated field types, and that each record
corresponds to a different person. This is typical of databases. Usually, a
record is about a unique entity such as a customer, business establishment,
inventory item, or property.
The contents of
each field type must follow certain rules.
Character - A combination of letters, numbers, space,
and/or punctuation marks that are treated as a test string. When a
string is used as part of a command, it is enclosed in single quotes, quotation
marks, or square brackets (‘text’ “text” [text]. If you wish to use one of
these punctuation marks (or delimiters) as part of a string. Enclose the
string with one of the other delimiters.
Example: “Enter
student’s name.”
If both a single
and double quote are used within the text of your prompt string, you can use
the bracket delimiter.
Date – An
8-character-wide field having the format mm/dd/yy. This can be modified to
other country formats with either SET DATE experession (Section 9) or by using
what is called a PICTURE clause (Section 7). The SET CENTURY ON displays the
entire year, i.e., mm/dd/yyyy (Section 9).
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