CREATE OR REPLACE FUNCTION VERIFICA_SEGMENTO_MERCADO
    (p_id in segmercado.id%type)
        RETURN boolean
IS
    v_dummy number(1);
BEGIN
    SELECT 1 into v_dummy
        FROM segmercado
        WHERE id = p_id;
    RETURN true;
EXCEPTION   
    WHEN no_data_found then
        RETURN false;
END;