How to Create an Index on Part of a Character Field

ID: Q98445

2.00 2.50 2.50a | 2.50 2.50a 3.00

MS-DOS          | WINDOWS

kbprg

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0
Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, and 2.5a
Microsoft FoxPro for Windows, versions 2.5 and 2.5a

If you want to create an index on part of a character field, you can create the index with the SUBSTR() function. The following code is used for indexing on the first five characters of a field called NAME:

   INDEX on SUBSTR(Name,1,5) TAG partnam

If the NAME field contains a last name and first name separated by a comma, indexing on the last name can be performed as follows:

   INDEX on SUBSTR(Name,1,(AT(",",Name,1)-1)) TAG lastname

However, if the above command is used, FoxPro will create an index tag that does not order the database accordingly. For example, with the NAME field in a five-record database as listed below

   Record 1: Brown, John
   Record 2: Williams, Mary
   Record 3: William, Bob
   Record 4: Willis, James
   Record 5: Williams, Mark
   Record 6: William, Bill

using the INDEX statement above will result in the database being ordered as follows:

   Record 1: Brown, John
   Record 2: Williams, Mary
   Record 3: William, Bob
   Record 5: Williams, Mark
   Record 6: William, Bill
   Record 4: Willis, James

To have the database ordered accordingly, you must use the PADR() function to pad the string returned by the SUBSTR() function with spaces equal to the length of the field. For example:

   INDEX on PADR(SUBSTR(Name,1,(AT(",",Name,1)-1)),15," ") TAG partnam

For more information, see the "Commands & Functions" manual for FoxPro version 2.0 or the "Language Reference" manual for FoxPro version 2.5.

Additional reference words: VFoxWin 3.00 FoxDos FoxWin 2.00 2.50 2.50a string KBCategory: kbprg KBSubcategory: FxprgGeneral

Keywords          : FxprgGeneral 
Version           : 2.00 2.50 2.50a | 2.50 2.50a 3.0
Platform          : MS-DOS WINDOWS