data have;
input height weight class $ id $;
cards;
156 51 Amber Chem101
156 52 Amber Math102
156 52 Amber Math102
167 54 Denise ENGL201
167 55 Denise ENGL201
145 56 Ginny CHEM101
145 57 Ginny ENGL201
145 58 Ginny MATH102
134 59 Lynn CHEM101
134 60 Lynn CHEM101
134 61 Lynn MATH102
178 62 Rick CHEM101
178 63 Rick HIST300
178 64 Rick HIST300
;
proc sql;
select class,sum(weight)/sum(height) as rate from have group by class;
quit;

太感谢了！能不能再请教个问题，我想把下面的观测值中height相同且weight为0的观测值删除（即第二条观测值）删除后，再做上面的操作，请问用怎么实现呢？
height weight class id
156 51 Amber Chem101
156 0 Amber Math102
156 52 Amber Math102
167 54 Denise ENGL201
168 0 Denise ENGL201
145 56 Ginny CHEM101
145 57 Ginny ENGL201
145 58 Ginny MATH102
134 59 Lynn CHEM101
134 60 Lynn CHEM101
134 61 Lynn MATH102
178 62 Rick CHEM101
178 63 Rick HIST300
178 64 Rick HIST300

data have;
input height weight class $ id $;
cards;
156 51 Amber Chem101
156 0 Amber Math102
156 52 Amber Math102
167 54 Denise ENGL201
168 0 Denise ENGL201
145 56 Ginny CHEM101
145 57 Ginny ENGL201
145 58 Ginny MATH102
134 59 Lynn CHEM101
134 60 Lynn CHEM101
134 61 Lynn MATH102
178 62 Rick CHEM101
178 63 Rick HIST300
178 64 Rick HIST300
;
proc sort data=have;
by height descending weight;
run;
data want;
set have;
by height descending weight;
if first.height then total=0;
total+1;
if weight=0 and total>1 then delete;
run;
proc sql;
select class,sum(height)/sum(weight) as rate from want group by class;
quit;

非常感谢！还希望以后跟着大师们多多学习呀！

真是不好意思，我能不能再问个问题，比如下面的数据，我想计算weight的和，但是weight和height的相等观测值，只统计一次（如第一条和第二、三条观测值只计算一次），请问怎么操作
height weight class id
156 51 Amber Chem101
156 51 Amber Math102
156 51 Amber Math102
167 54 Denise ENGL201
168 0 Denise ENGL201
145 56 Ginny CHEM101
145 57 Ginny ENGL201
145 58 Ginny MATH102
134 59 Lynn CHEM101
134 60 Lynn CHEM101
134 61 Lynn MATH102
178 62 Rick CHEM101
178 63 Rick HIST300
178 64 Rick HIST300