SELECT * FROM stu
ORDER BY classid, studentid;

------解决方案--------------------
SQL code
SQL> with TAB as
  2  (select  1 cid,1 sid,'张三' name from dual
  3  union all
  4  select  2 cid,2 sid,'李四' name from dual
  5  union all
  6  select  1 cid,3 sid,'王五' name from dual
  7  union all
  8  select  3 cid,4 sid,'王二' name from dual
  9  union all
 10  select  2 cid,5 sid,'小李' name from dual)
 11  select * from TAB order by cid,sid;
 
       CID        SID NAME
---------- ---------- ----
         1          1 张三
         1          3 王五
         2          2 李四
         2          5 小李
         3          4 王二
 
SQL>

------解决方案--------------------
SQL code
select * from tname order by classid,studentid;