一： oracle数据库写法：
1：select * from (select rownum rn ,* from 表名 wher rownum<20) a
where a.rn>10
2：select * from 表名 where rownum<20
minus
select * from 表名 where rownum<10
二：SqlServer数据库写法：
1:select top 20 * from tablename where id not?exists (select top 10 * from tablename)//前20条记录再过滤掉前10条
2:select top10 * from (select top 20 * from order by column) order by column desc//子查询中取20条倒序，然后从子查询中取前10条
三：mysql的写法：
select * from tablename where LIMIT 9,10