Can only one of using and or be selected in leftjoin?

http://www.cnblogs.com/hhqinliang/p/8871802.html http://www.cnblogs.com/hhqinliang/p/8872874.html http://www.cnblogs.com/hhqinliang/p/8871842.html http://www.cnblogs.com/hhqinliang/p/8871849.html