Hello. i have problem when running risk set sampling macro. i  found this macro on this(http://mchp-appserv.cpe.umanitoba.ca/Upload/SAS/risk_set_sampling_macro.sas.txt)   this is my marco typing on SAS %risk_set_match (cohort_name = CASE_CTRL,                        outcome_var = outcome,                        end_fu = END_EPI,                        randnum = 123,                        K = 20,          control_index_dt = case_fu,          rs_match_where = a.sex=b.sex          id = JID,          time0 = START_EPI,          gender = sex,          agevar = age,          output_name = matched1,          no_match = N                       );   In the middle of macro, there is -----------------------------------------------------------    proc sql;       create table risk as       select     a.&id. as case_ID,              b.&id. as control_ID,     a.&agevar. as case_age,           b.&agevar. as control_age,              a.&gender. as case_sex,              b.&gender. as control_s,              a.&time0. as case_t0,              b.&time0. as control_t0,           a.&end_fu. as case_endfu,              b.&end_fu. as control_endfu,           a.caco as case_caco,           b.caco as control_caco,              a.index_date,              a.match_num       from case_caco1_I a,            controls b       where &rs_match_where;    quit;    proc append base = risk_set data = risk;    run; ---------------------------------------------------------------- In here such as case_ID, from ~~~, i have got errors. ERROR 22-322 ~~~~   please answer me TT   ... View more