How to Perform REPLACE for Two Databases w/ Common Field

• Microsoft Visual FoxPro for Windows, version 3.0
• Microsoft FoxPro for Windows, versions 2.5x, 2.6x
• Microsoft FoxPro for MS-DOS, versions 2.5x, 2.6x
• Microsoft FoxPro for Macintosh, versions 2.5x, 2.6a

SUMMARY

To update more than one record in a database from another, similar database, you may need to check for an end-of-file (EOF) marker during each iteration of the REPLACE operation. This is best accomplished with a DO ... WHILE loop, as demonstrated below.

NOTE: In order for this process to work, the two databases must have a common key field.

MORE INFORMATION

To demonstrate this process, we'll use the CUSTOMER database in the FoxPro TUTORIAL subdirectory. First, we'll copy CUSTOMER to a new database called NEWCUST, then we'll delete the contents of the COMPANY field, and then we'll restore the contents of the COMPANY field using the COMPANY field information in CUSTOMER.

1. Set the default directory to the location of CUSTOMER.DBF. For example, in FoxPro 2.x, issue the following command in the Command window:

         SET DEFAULT TO C:\<FoxPro_directory>\TUTORIAL.
   

       In Visual FoxPro, Issue the following:
   

         SET DEFAULT TO C:\<FoxPro_directory>\SAMPLES\DATA
   

       NOTE: In Visual FoxPro, you will also need to change all references
       below from from CNO to CUST_ID.
   

2. In the Command window, issue the following commands:

         USE customer
         COPY TO newcust
         SELECT 0
         USE newcust
         ** the following command has no spaces between the quotation marks
         REPLACE ALL company WITH ""
         ** BROWSE the table with the empty COMPANY field contents
         BROWSE
         CLEAR ALL
         CLOSE ALL
         ** open a new program file called TEST
         ** if a program called TEST already exists, choose another name
         MODIFY COMMAND test
   

3. In the edit window for the TEST program, type the following commands:

         SELECT 0
         USE customer
         SELECT 0
         USE newcust
   

         SELECT customer
   

         ** while not at end of file of CUSTOMER, do some actions
         DO WHILE !EOF()
            ** select the destination table
            SELECT newcust
            ** replace the empty COMPANY field with data from CUSTOMER where
            **   the common key field is the same
            REPLACE newcust.company WITH customer.company;
               FOR newcust.cno = customer.cno
            ** select the source table again to go to next record
            SELECT customer
            SKIP
         ENDDO
         SELECT newcust
         ** BROWSE the table with the newly filled COMPANY data
         BROWSE
   
      NOTE: If the first database (that is, CUSTOMER) is indexed on the common
      key field between the two tables, replace the commands in step 3 with
      the following:
   
         SELECT 0
         USE customer ORDER TAG cno
         SELECT 0
         USE newcust
         REPLACE ALL newcust.company WITH customer.company FOR ;
            seek(cno,"customer")
   
   

4. Save TEST.PRG and then run it.

REFERENCES

"Language Reference," (Windows and MS-DOS) pages L3-312, L3-470, L3-480, L3- 816, L3-861, L3-1040, L3-1108

"Language Reference," (Macintosh) pages 271, 396, 404, 651, 685, 827, 884