>>BTW, when you were creating this constraint, you created it for the specific key? So, start from that key first.
>
>I am confused. How can I create a constraint NOT for a specific key? What I did is
>1. Created foreign key constraint on field MyField1
>2. Created foreign key constraint on field MyField2
>and so on.
>but when I try to do it for some field MyFieldN I was hitting the problem.

That's the point. The FieldN which references FieldM in another table is a problem. Start from investigating FieldM that FieldN was trying to reference.