group by 1,2,3,4的含义

Question

有人可以向我解释下面的代码吗？我被Group by 1,2,3,4混淆了,因为没有变量和值叫1,2,3,4.

proc sql; create table SampleData as select
uniqID, Category, Grade, Value,

count(uniqID) as CNT,
avg(PRICE) as APR,
avg(Value) as ALE

from DataIn where date ge &intdt. group by 1,2,3,4;
quit;

Answer 1

它是select语句中第1,第2,第3和第4个变量的相对引用.IE浏览器.uniqID,类别,等级,价值.