create table supplier  (    supplier_id numeric(10) not null,    supplier_name varchar2(50) not null,    contact_name varchar2(50),    constraint u_supplier_id unique(supplier_id)  );  end;    create table supplier  (    supplier_id numeric(10) not null,    supplier_name varchar2(50) not null,    contact_name varchar2(50),    constraint u_supplier unique(supplier_id, supplier_name)  );  end;    declare    v_supplier_name supplier.contact_name%type;  begin    select user    into v_supplier_name    from dual;    insert into supplier    (      supplier_id,      supplier_name,      contact_name    )    values    (      seq_supplier_id.nextval,      v_supplier_name,      'Test'    );  end;   select * from supplier;