>>>>Is it a typo? You put ID.grno instead of ID1.grno
>>>>
>>>>Also check if you have rules or triggers in PS1 table.
>>>>
>>>Thanks, it was typo when I simplified the UPDATE statement. NO rules or triggers in the tables.
>>
>>The statement looks OK to me - are you sure you're updating the table you are thinking you're updating? Could it be another table included into exe or somewhere else in the path?
>>
>>You may also try using replace command instead.
>
>I updated the right table, because when I ignored the error message, the data is there.
>Yes, I can use the replace command.
>Thanks

It could have also been a bug in VFP, but even if it is, there is no chances it will be corrected.