How do I compare new data with old data to find differences?

Assume there are two student tables: student1(id char(5),name char(20)); student2(id char(5),name char(20)); You can find students who have the same name but different ids by using the following command:

dmSQL> select student1.id,student2.id,student1.name

    2>   from student1,student2

    3>   where student1.name=student2.name and

    4>         student1.id<student2.id;