What if there was not always +1? data A ; input CM15 case_nbr $ Action_dt : mmddyy12.; format Action_dt  mmddyy10.; cards; 1234 A1234 1/1/2015 1235 A1235 1/12/2015 1236 A1236 1/20/2015 1237 A1237 1/20/2015 1238 A1238 1/23/2015 ; run;   data B ; input CM15 action_dt : mmddyy12.; format Action_dt  mmddyy10.; cards; 1234 1/1/2002 1234 1/2/2015 1234 1/30/2015 1235 1/13/2015 1235 2/1/2015 1236 1/20/2015 1237 1/21/2015 1238 2/6/2015 ; run; proc sql; create table want(drop=dif) as   select a.*,b.action_dt as action_dt_2 ,(b.Action_dt-a.Action_dt) as dif    from a left join b on a.CM15=b.CM15     where calculated dif gt 0 or calculated dif is missing   group by a.CM15    having calculated dif=min(calculated dif); quit; Xia Keshan ... View more