How to create groupid with muti cols

[stataq]

Hello All, 

I'm trying to assign unique id based on the info from var1 and var2. Not sure how to do it.  New variable 'id' will restart from 1 when var1 changed.

sample data:

data have;
input var1 var2;
datalines;
1 1
1 1
1 3
2 1
2 2
2 2
2 5
;
run;

Thank you! 

[PaigeMiller · Accepted solution]

This is why Fred Flintstone invented the FIRST. and LAST. structures for SAS data steps.

data want;
    set have;
    by var1 var2;
    if first.var1 then id=0;
    if first.var2 then id+1;
run;