The DBF file type is for dBase II and dBase III files. The DBF4 file type is for dBase IV files.
Suppose you have a dBase IV file on a floppy disk which contains 10,000 sales transactions for 1986. You want to LOAD that file into the SALES table in your database. The file name is 86SALES.DAT.
The Record Description to describe this file might be:
RD JACK DBF4 The name of the Record Description is
filler x(1) JACK. The file type is DBF4 which indi-
store# x(3) cates a dBase IV file. The data definition
store_name x(12) statements consist of field names, type,
mo x(2) and sizes that comprise a typical record
dy x(2) in the file 86SALES.DAT. The FILLER x(1)
yr x(4) accounts for the first character of each
cust# x(6) record, which is an internal dBase "flag"
cust_name x(30) for each data record.
street x(20) city x(20) Here is a tip: In the RD field descriptions
state x(2) for DBF files, it is most likely that all
zip x(5) data types will be either x(n) or x(n.f)
item# x(6) such as x(10) or x(8.2). See the topic
descr x(20) Data Types and Rules for Data Transfer
.
quan_bot x(4)
price x(6.2)
Lets look at the relationship between the RD in the Application Interface and the SALES table in the database:
RD JACK DBF4
filler x(1) TD SALES 50000 Records
store# x(3) store# x(3) key
store_name x(12) item# x(6) key
mo x(2) cust# x(6) key
dy x(2) pdate date key
yr x(4) :1 yr x(4) key
cust# x(6) :1 mo x(2) key
cust_name x(30) :1 dy x(2)
street x(20) descr x(20) key
city x(20) quan_bot n(4)
state x(2) price n(5.2)
zip x(5)
item# x(6)
descr x(20)
quan_bot x(4)
price x(6.2)
Now you are ready to load the 10,000 external records from the diskette in drive A. The LOAD command is
LOAD SALES JACK a:\86SALES.DAT
(tablename) (rdname) (filename)
The Primary Rule For Data Transfer is
Where the names match, data moves. Differences in field size, type, and the order in which the fields appear are handled automatically when the data transfers. See Data Types and Rules for Data Transfer
.
Consider what was left behind in our sample file transfer.
For any field in the RD where there is no corresponding field name in the database table, no data transfered. You can see several fields in the RD where data was left behind. The data base field named PDATE gets its value because data transferred into each of the elementary fields that it is composed of.
Export
An RD with DBF or DBF4 file types can be used to LOAD or UNLOAD data. To UNLOAD the content of the SALES table to a diskette on drive A, issue the following commands:
FILL A SALES
UNLOAD A SALES MARY A:\SALES86.DAT
A file named SALES86.DAT is created on drive A. It is a dBase IV file with fixed length records. The Record Description MARY might look like this:
RD MARY DBF4
filler x(1)
store# x(3)
item# x(6)
cust# x(6)
mo x(2)
dy x(2)
yr x(4)
descr x(20)
quan_bot x(6)
price x(8.2)
All of the data in the SALES table "unloads," as there is a corresponding name in the RD for all of the fields in the SALES table. There is more detailed information available about data transfer. See Rules for Data Transfer
.
