删除没用的书籍版块及相关内容，此部分内容已经在书籍站里。

select * from ty_main 
where site_id=111 and forum_type='5'
--521
select forum_id from ty_main 
where site_id=111 and forum_type='5' limit 10
group by forum_id

select * from ty_post where main_id in 
(select main_id from ty_main 
where site_id=111 and forum_type='5') limit 10
--28
select forum_id from ty_forum
where site_id=111 and forum_type='5'
group by forum_id
--31

--删除
delete from ty_forum where site_id=111 and forum_type='5';
delete from ty_post where main_id in 
(select main_id from ty_main 
where site_id=111 and forum_type='5');
delete from ty_main 
where site_id=111 and forum_type='5';