Oracle高效分页查询

1. 无ORDER BY排序的写法。(效率最高)
   (经过测试，此方法成本最低，只嵌套一层，速度最快！即使查询的数据量再大，也几乎不受影响，速度依然！)

    SELECT *
      FROM (SELECT ROWNUM AS rowno, t.*
              FROM emp t
             WHERE hire_date BETWEEN TO_DATE ('20060501', 'yyyymmdd')
                                 AND TO_DATE ('20060731', 'yyyymmdd')
               AND ROWNUM <= 20) table_alias
     WHERE table_alias.rowno >= 10;
   

2. 有ORDER BY排序的写法。(效率最高)
   –(经过测试，此方法随着查询范围的扩大，速度也会越来越慢哦！)

    SELECT *
      FROM (SELECT tt.*, ROWNUM AS rowno
              FROM (  SELECT t.*
                        FROM emp t
                       WHERE hire_date BETWEEN TO_DATE ('20060501', 'yyyymmdd')
                                           AND TO_DATE ('20060731', 'yyyymmdd')
                    ORDER BY create_time DESC, emp_no) tt
             WHERE ROWNUM <= 20) table_alias
     WHERE table_alias.rowno >= 10;