Maximo valor de campo en varias tablas

[the_web_saint]

Creo que aplicando el mismo order by desc limit 1 en cada unos de los select funcionaria verdad?:

(SELECT num_order from tbl_text where id_columna = 6 ORDER BY num_order desc limit 1)
union all
(SELECT num_order from tbl_textbox where id_columna = 6 ORDER BY num_order desc limit 1)
union all
(SELECT num_order from tbl_file where id_columna = 6 ORDER BY num_order desc limit 1)
union all
(SELECT num_order from tbl_menu where id_columna = 6 ORDER BY num_order desc limit 1)
union all
(SELECT num_order from tbl_radio where id_columna = 6 ORDER BY num_order desc limit 1)
union all
(SELECT num_order from tbl_checkbox where id_columna = 6 ORDER BY num_order desc limit 1) ORDER BY num_order desc limit 1