data temp1;
input a $1. b $1. c $1.;
cards;
111
111
111
112
112
112
122
122
122
;
run;
data temp1;
set temp1;
cls=compress(a||'*'||b||'*'||C);
run;
proc sort data=temp1;
by cls;
run;
data temp1;
set temp1;
by cls;
if first.cls then flag=1;
else flag+1;
run;

data work.a;
        input a b c;
        datalines;
1 1 1
1 1 1
1 2 3
1 2 3
1 3 4
1 1 1
1 1 2
1 1 2
1 1 2
1 2 2
1 3 4
1 2 2
1 2 2
;
run;

proc sort data = work.a;
        by a b c;
run;

data work.b;
        set work.a;
        by a b c ;
        if first.c then do;
                flag = 1;
        end;else do;
                flag +1 ;
        end;
run;

楼上的
if first.c 不保险
举例如数据
111
111
111
121
121
122
122
123

他的理解是对的。利用first.x是好的选择。京剧

后来想想其实 if first.a=1 or first.b=1 or first.c=1 then flag=1; 更简洁

proc sort data=temp1;
by a b c;
run;

data temp1;
set temp1;
by a b c;
if first.a=1 or first.b=1 or first.c=1 then flag=1;
else flag+1;
run;