今天在csdn上看到一篇报道，关于如何甄别面试者的一些技巧，发现了几个知识点，总结了一下
(1)select *from talbeA as a left join tableB as b on a.key=b.key (2)select *from talbeA as a left join tableB as b on a.key=b.key where b.key is null (3) select *from talbeA as a inner join tableB as b on a.key=b.key (4)select *from talbeA as a right join tableB as b on a.key=b.key (5)select *from talbeA as a right join tableB as b on a.key=b.key where a.key is null (6)select *from talbeA as a outer join tableB as b on a.key=b.key (7)select *from talbeA as a outer join tableB as b on a.key=b.key where a.key is null and b.key is null
原文：http://www.cnblogs.com/alphafly/p/3999676.html