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转自：http://blog.csdn.net/winter3125/archive/2009/12/18/5032871.aspxtable a(id, type):id type----------------------------------1 12 13 2table b(id, class):id class---------------------------------1 12 2sql语句1：select a.*, b.* from a left join b on a.id = b.id and a.type = 1;sql语句2：select a.*, b.* from 阅读全文
