Article: Q135753
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s):
Keyword(s):
Last Modified: 15-FEB-2000
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual FoxPro for Windows, version 3.0
-------------------------------------------------------------------------------
SUMMARY
=======
Because Data Validations are expressions, NULL values inserted into fields and
passed to Data Validation expressions behave in a consistent manner with that of
other expressions. If the Data Validation for a field resolves to True (.T.) or
False (.F.) with a NULL value, that logical result is accepted. In many cases,
the expression will evaluate to NULL (For example, NULL > 1000). In this
case, because the expression returns NULL, not True or False, it is rejected.
MORE INFORMATION
================
Step-by-Step Example
--------------------
1. Create a program called Myprog.prg
2. Type in the following code segment:
CREATE DATABASE mydata1
CREATE TABLE mytable (lastname c(20) NULL, firstname c(20) NULL, ;
city c(20) NULL CHECK city>"a")
INSERT INTO mytable (lastname,firstname,city) ;
VALUES ("Ansarti","Jim","San Jose")
INSERT INTO mytable (lastname,firstname,city) ;
VALUES ("Hayden","Rance",.NULL.)
INSERT INTO mytable (lastname,firstname,city) ;
VALUES ("Putnam","Phil","New Orleans")
3. Save the program.
4. In the Command window, type:
DO Myprog.prg
5. The program executes, and the INSERT command with city equal to .NULL.
generates the error message, "Field City Validation rule is violated."
Additional query words: 3.00 VFoxWin
======================================================================
Keywords :
Technology : kbVFPsearch kbAudDeveloper kbVFP300
Version : WINDOWS:3.0
=============================================================================