同时打开3个表的sql语句

用关联查询，必须在数据库中建立关系吗？
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我做了个会员管理，在资料修改时，需要根据Session("UserName")打开3个表
1）UserInfo(会员资料表) UserId,UserName,UserProvinceId,UserCityId等
2）UserProvince(会员所在的省份) UserProvinceId,UserProvinceName
3）UserCity(会员所在的城市) UserCityId,UserCityName

如何根据Session("UserName")，把会员资料，和UserProvinceName
，UserCityId,UserCityName通过一个语句提取出来啊
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select a.userid as userid,a.username as username,b.userprovincename as userprovincename,b.usercityid as usercityid,c.usercityname as usercityname from userinfo a,userprovince b,usercity c where a.username=session("username") and a.userprovinceid=b.userprovinceid and a.usercityid=c.usercityid
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select a.*,b.userprovincename as userprovincename,c.usercityname as usercityname from userinfo a,userprovince b,usercity c where a.username=session("username") and a.userprovinceid=b.userprovinceid and a.usercityid=c.usercityid