Make Rating field Unique ( create a Index and allowduplicates : No) in your master Rating form.
Could you please explain more? Do you want rating to be unique in Rating Master form?? If yes then it should work..
Can you explain it in detail?
Did u create the index in the table and add the field rating name make the property Allow duplicates to No.
This didnt work..Check it once.i think you didnt make property to no.
You can build an Unique Index on that field
or you can override the valildate Write method(Table level) and check whether entered value exists or not - if exists throw error.
Does the index is enabled? Which field you have added to the Index?