楼主是不是想用proc compare？

proc compare base=dat13 compare=dat14 out=result(drop=_type_ _obs_) noprint;
id city;
run;

用了compare，但输出只有记录集的比较而已

用SQL
proc sql;
create table xx as select a.*, b.y1 as by1, b.y2 as by2, b.y3 as by3, a.y1-b.y1 as dy1, a.y2-b.y2 as dy2, a.y2 -b.y2 as dy2
from dat13 as a left join dat14
on a.city=b.city;
--------------------------------------------
或用 merge by city 后, 再计算
PROC SORT DATA=dat13 OUT=dat13;
  BY city;

proc dat14A;
set dat14(rename=(y1=b_y1 y2=b_y2 y3=b_y3));

PROC SORT DATA=dat14A OUT=dat14A;
  BY city;
RUN;

DATA dat2 ;
  MERGE dat13 dat14A;
  BY city;
RUN:

Data dat22;
  set dat2;
  dy1=y1-by1;
  dy2=y1-by2;
  dy3=y1-by3;
  
run;

我记得在difference中会有对应记录的单个变量的值的不同的显示，diff之类的
如果需要的是数据集的话好像可以通过ods output输出

我觉得可能看起来有些简陋……