oracle row_number() over ,rank() over ,dense_rank() over ,keep 函数比较
create table test2 as select 1 id, 111 mc,1 sl from dual union all select 1 , 222,6 from dual union all select 1 , 333,2 from dual union all select 1 , 555,3 from dual union all select 1 , 666,3 from