Unable to insert into a table through FormView Control

 Hi all
I created a table that has no primery key.
I'm sure that I must not assign a primary key to any field because this table will have repeated values.
Anyhow, when I link the FormView control to this table through DataSource, it doesn't accept to allow Insert,Update,Delete.
I tried to assigned the primary key property to one field in the table, in that case only it allowed Insert,Update,Delete.
My question is how can I Allow Insert,Update,Delete operations of FormView Control onto a table that has no primary key.
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