三表查询的问题

Question

三张表 downloadlogs_day : id,downloadtime时间,ipaddress网关地址,filename所下载的文件名称,downloadnumber一分钟内该网关下载的次数

 

ipaddressmappings : id,ipaddress网关地址,area网关所属地区，国家，省份

 

 filesupportmobile: id,filename文件名称,mobiletype手机终端类型agent

 

我想联合这三张表查询 所有地区，按日分组的 下载次数

sql :

SELECT d.downloadtime ,'全部' as mobiletype,sum(d.downloadnumber) as number FROM downloadlogs_day as d ,filesupportmobile as f ,ipaddressmappings as i where f.filename = d.filename and d.ipaddress = i.ipaddress and d.downloadtime >= '2009-06-15' and d.downloadtime <= '2009-06-19'
group by d.downloadtime order by downloadtime

 

上面这条sql的查询结果一天一变化，就是昨天查到的结果和今天查到的结果不一样，请大家看看问题出在什么地方。谢谢

Answer 1

从你查询的返回字段来看，有必要多表连接吗？

如果非得用多表连接，注意看下 filesupportmobile.filename 与 ipaddressmappings.ipaddress 是否是unique，是否有增减