MySql级联查询join on的实例

SELECT DISTINCT u.`name` FROM eclass_user AS u JOIN eclass_testrecord AS t ON(u.userID=t.userID) WHERE t.testID IN (220,256,257);

这个是三张表的级联查询，和下面的差不多关键字用的也是一样的

SELECT DISTINCT u.`name` FROM user AS u JOIN test AS t ON(t.userID=u.userID) WHERE t.paperID IN(79,139,152,140);

这个是两张表的级联查询，包括去重关键字和in关键字。