How to Preserve Index Expressions to Rebuild CDX and Tags

MORE INFORMATION

Sample Code

* Make the CDX Expression table.

CREATE TABLE cdxexp ;
   (TAG C(10),expression C(254))

* Insert three index expressions into the table.
* Below is a simple index expression on one field.

INSERT INTO cdxexp ;
   (TAG,expression) ;
   VALUES ;
   ("COMPANY","company")

* Below is a concantenated index expression.

INSERT INTO cdxexp ;
   (TAG,expression) ;
   VALUES ;
   ("STATE_CO","ALLTRIM(UPPER(state))+ALLTRIM(company)")

* Below is a complex index expression that correctly orders a numeric
* field concantenated with a character field. Indexing on the STR() of
* a numeric alone will yield incorrect ordinal values of the numeric
* field. This expression uses PADL and ALLTRIM with STR to put the
* numeric characters into the correct location in the string.

INSERT INTO cdxexp ;
   (TAG,expression) ;
   VALUES ;
   ("YTDP_ST","PADL(ALLTRIM(STR(ytdpurch,20,2)),20,'0') + ;
   ALLTRIM(UPPER(state))")

* Use the library FoxTools for the MessageBox function.

SET LIBRARY TO foxtools
SET DEFAULT TO c:\fpw26a\tutorial

* Delete the current CDX file in order to rewrite the header.

IF USED('CUSTOMER')
   SELECT CUSTOMER
   USE
ENDIF
DELETE TAG ALL

* Open the table to reindex (CUSTOMER.DBF) in the second Workarea.

SELECT B
USE C:\FPW26A\TUTORIAL\CUSTOMER

* Call the MsgBox function from FoxTools with "Yes/No" buttons, option 4.
* The MsgBox function will need to be replaced with a GET object for
* versions other than Windows.

msg="Ready to rebuild the CDX file?"
answer=MSGBOX(msg,"",4)

* If the user clicks the Yes button, the return value will be 6.

IF answer=6
   SELECT A                  && index expression file called "cdxexp"
   GO TOP
   DO WHILE NOT EOF()        && process the whole file
      mtag=cdxexp.tag        && read the values from the record
      mexp=cdxexp.expression
      SELECT B
      INDEX ON &mexp TAG &mtag   && index on the variable expressions
      SELECT A
      SKIP                   && go to the next record
   ENDDO
ENDIF

* End of program.