三个数据表的连接

select qr_train.train_name,qr_train.train_team,qr_train.train_workdiary,qr_train.train_note,qr_train.train_workfinish,qr_train.train_attend,qr_train.train_fault,
                qr_dorm.dorm_back, qr_dorm.dorm_sleep, qr_dorm.dorm_chucao, qr_dorm.dorm_qingjia, qr_dorm.dorm_safe,qr_behave.be_chat,
qr_behave.be_game,qr_behave.be_movie,qr_behave.be_novel,qr_behave.be_surf from qr_train,qr_dorm,qr_behave where qr_train.train_personid= qr_dorm.dorm_personid=qr_behave.be_personid  我想实现三个表连接，可是报错，请各位看看。