sql循环查询

场景：Sql循环查询（急），高手帮帮忙,该如何解决

Sql循环查询（急），高手帮帮忙
我循环读取新闻，有两个表，类别表和新闻表
class: c_id,C_name

news: n_id,n_name,c_id

我现在的要求是读出类别名称和下面的20条新闻

我之前是这样写的

select c_id,c_name From class
do while not rs.eof
读出名字：rs("c_name")
"select top 20 n_name from new where c_id="&rs("c_id")
do while Not N_Rs.Eof
读出新闻
n_rs.movenext
loop
rs.movenext
loop
这样写是最笨的现在数据量大了要多读好多条Sql 语句数度很慢有好点的查询方法吗？？
在线等急啊。。。。

------解决方案--------------------

SQL code

select a.* from 
(
  select c_name,n_name from class,news where class.c_id = news.c_id
) a 
where n_name in (select top 20 n_name from 
  (
     select c_name,n_name from class,news where class.c_id = news.c_id
  ) b where c_name=a.c_name ) 
order by a.c_name,a.n_name

------解决方案--------------------
--每個類別下的20條？

select a.C_name,b.n_name from  class a,news b
where a.c_id=b.c_id
and b.n_id in (select top 20 n_id from news where c_id=a.c_id order by n_id desc)
order by a.c_name,b.n_id desc

------解决方案--------------------

SQL code

select n_id, n_name, C_name 
from (select * from news N where (select count(1) from news where c_id=N.c_id and n_id>N.n_id)<20) News
  join class on News.c_id=class.c_id
order by N.c_id,N.n_id desc

相关推荐