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Comparing to NULL
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General information
Forum:
Visual FoxPro
Category:
Other
Environment versions
Visual FoxPro:
VFP 9 SP1
Miscellaneous
Thread ID:
01243011
Message ID:
01243024
Views:
29
>>>
>>>Then wouldn't just a simple IF (VARTYPE(OLDVAL(FIELD(i))<>VARTYPE(EVALUATE(FIELD(i))) be sufficient, or do you need to know when character (or other type) value changes, too?
>>
>>No, this would not work for me. The comparison should work on many different fields. Some fields will change the value but the type will be still be the same. The above expression will not pick up those cases.
>
>If a change in type is detected, that can only be to/from "X" (.NULL.). You could have a secondary check if you need to also know the value has changed (while it remains the same type).

I see. But the following also works (unless you see something I am missing):
IF (!ISNULL(EVALUATE(FIELD(i))) AND ISNULL(OLDVAL(FIELD
(i), "V_V_MYTABLE"))) OR ;
(ISNULL(EVALUATE(FIELD(i))) AND !ISNULL(OLDVAL(FIELD
(i), "V_V_MYTABLE"))) OR ;
!(EVALUATE(FIELD(i)) == OLDVAL(FIELD(i), "V_V_MYTABLE"))
Thank you.
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