Here's what MSDN Library (on-line Help) has to say:
Null Value Handling
Visual FoxPro provides support for null values. This support simplifies the task of representing unknown data and makes it easier to work with Microsoft Access or SQL databases that may contain null values.
Null values are:
Equal to the absence of any value.
Different than zero, the empty string ("", or blank.
Sorted ahead of other data.
Propagated in calculations and most functions.
Null values affect the behavior of commands and functions, logical expressions, and parameters.
Visual FoxPro support for null values complies with ANSI standards and affects any area of the product where values and expressions are used.
Using NULL in Values and Expressions
In Visual FoxPro, you assign the null value programmatically with the .NULL. token or interactively with CTRL+0 in a field. Note that the periods around .NULL. are optional. To detect whether a field or variable contains a null value, or whether an expression evaluates to a null value, use ISNULL( ).
See Also
Behavior of Null Values in Logical Expressions | Behavior of Null Values in Commands and Functions | EMPTY( ) Function | ISBLANK( ) Function | ISNULL( ) Function | NULL as a Parameter | NULL as a Value | Data Manipulation
Hope this will help. You might want to find it yourself in your own MSDN Librar (should be provided on CDs when you buy MS VS 6.0 or VFP 7.0) and follow the thread there.
To be exact, that doesn't change the NULL to zero. The field or variable will still contain NULL, but the user will see it as zero.
Mike Lewis
Edinburgh, Scotland
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