1.the group by expr can be expression,but the expr in select_list which
doesn't contain agg_func must be in the group by as the same form.
eg:select row_id%2 from NATION group by row_id%2;
2.The select_expr of the subquery in from_list must has alias,and the
subquery can be regarded as the base_table.
eg:select a,row_id from (select row_id as a from NATION where
row_id<10)as na,NATION where a=row_id;