Subject getting error when creating unique constraint
Author zifnabbe

I get the following error when I try to create a unique constraint,
what does it mean? :

ISC ERROR Code 335544349

attempt to store duplicate value (visible to active transactions) in
unique index "RDB$INDEX_16"

I've emptied the table on which I want to put that constraint and
I've nowhere set already such a unique constraint...

Thanks, tom.