CREATE TABLE z_test(id VARCHAR2(5), val VARCHAR2(5))
/
--v forme block1.item1 is z_test.id; block1.item2 is z_test.val
begin
    insert into z_test(id, val)
    select :block1.item1, :block1.item2
    from dual
    where not exists(select 1 from z_test where val = :block1.item2);
        
    if(sql%rowcount = 0)then
        --record is found
        --error;
        null;
    end if;

end;

type r_block is record(
  id 		number, 
  field_1 	varchar2(100)
);
type t_block is table of r_block index by pls_integer;

procedure slc_block(p_t in out nocopy t_block, p_id number);  
procedure upd_block(p_t in out nocopy t_block);  
procedure ins_block(p_t in out nocopy t_block);