1.字符串类型字段 区分大小写 where table_name = 'MIDDLE'
2.execute immediate '' bulk collect into v_xxx_tab
3.列别名不加引号 select count(1) 计数
4.select distinct max(personincome) over (partition by earnmonth, earn) from earnings 需要加distinct 。这里的 partition by不同于 group by
5.order by null last / null first