下面语句:
select "name","class","score" from score_tbl where "score" > 80 group by 1,2
等价于:
select "name","class","score" from score_tbl where "score" > 80 group by "name","class"
含义:
"group by 1,2"的意思是说:按照select后面参数的第1列、第2列分组(从1开始计算,不含0)