DELETE falta_histo_mat.* FROM falta_histo_mat, periodo  p 
				WHERE cod_mat=6 AND tip_fal='t' AND id_alu in(1088972028,1088972028,1088972028) AND (p.id_peri=1 AND fec_fal>=  p.fec_ini and fec_fal<=fec_cor_tot)  