如何理解SQL中的自连接？
复制SELECT s1.Sname AS Sname1,何理 s2.Sname AS Sname2 FROM Student s2,Student s1 1.2.3.4.
复制SELECT s1.Sname AS Sname1,何理 s2.Sname AS Sname2 FROM Student s2,Student s1 1.2.3.4.
复制SELECT s1.Sname AS Sname1,何理 s2.Sname AS Sname2 FROM Student s2,Student s1 1.2.3.4.