高手，你好！目前我用的表比较大，用LEFT JOIN比较费时间，可否只操作一张表来实现这个过程？谢谢！

Try this:

data test01;
        input id1 $ id2 $ @@;
cards;
A A
A A
A A
A B
A C
B C
B D
B D
C F
C F
C G
;run;

proc sort data = test01;
        by id1 id2;
run;
data test02;
        set test01;
        by id1 id2;
        if first.id1 then dis = 0;
        if first.id2 then dis + 1;
run;

Clever Guy! Thanks.

data a;
input x $ y $ @@;
cards;
A A
A A
A A
A B
A C
B C
B D
B D
C F
C F
C G
;run;

proc sort data = a;
by x y;
run;

DATA b;
SET  a;
BY X Y;
IF first.x and first.y then INDEX=1;
ELSE if first.y then INDEX+1;
RUN;