update tb_vnd_item set
    vl_cst_med = tb_item_emp.vl_cst_med,
    vl_cst_rep = tb_item_emp.vl_cst_rep
from tb_item_emp
where
    tb_item_emp.id_emp = tb_vnd_item.id_emp and
    tb_item_emp.id_item = tb_vnd_item.id_item;