SAS PROC SQL -- merging and calculation

proc sql ;
create table new as
select a._Material_Substance_Use_Abuse,
(a._1_Yes+a._2_No) as total_n, a._1_Yes as Yes_n, a._2_No as No_n,
a._3_Section_not_available as No_no_section,
(a._1_Yes/(a._1_Yes+a._2_No)) as YES_percentage_wo_sec,
(a._1_Yes/(a._1_Yes+a._2_No+a._3_Section_not_available)) as YES_percentage_w_sec
from Eye_twoT1 AS a
;