精典SQL语句

分类统计总数并排序多表联合查询的两种方法
例:
查询地区表中各省下面城市总数,并对查询结果取前十名
法一:
select b.id,a.[name],b.counts from n_area a,(select top 10 parent_id as id,sum(parent_id) as counts from n_area where parent_id<>0 group by parent_id order by sum(parent_id) desc
) b where a.id=b.id
法二:
select top 10 a.id,a.[name],(select count(*) from n_area b where b.parent_id=a.id ) as counts from n_area a where a.parent_id=0 order by counts desc
例:
查询发贴表中回复数最多的前十条发贴,(发帖与回帖同一表,查询出发帖主题,发帖ID,发帖人(另表),回帖数)
select a.mid,a.mtitle,(select c.uimg from BBS_Power c where c.uid=a.uid and c.uclass=a.uclass) as img from BBS_Msg a,(select top 10 partenID as id,sum(partenID) as counts from BBS_Msg  where partenID<>0 group by partenID order by sum(partenID) desc) b where a.mid=b.id