Oracle分页查询

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一、利用rownum，无order by(最优方案)

      如下例查询出来5003行数据，然后扔掉了前面5000行，返回后面的300行。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 XXX t

         WHERE hire_date BETWEEN TO_DATE (‘20060501‘, ‘yyyymmdd‘)

                             AND TO_DATE (‘20060731‘, ‘yyyymmdd‘)

           AND ROWNUM <= 20) table_alias

 WHERE table_alias.rowno >= 10;

SELECT *

  FROM (SELECT a.*, ROWNUM rn

          FROM (SELECT *

                  FROM table_name) a

         WHERE ROWNUM <= 40)

 WHERE rn >= 21

其中最内层的查询SELECT * FROM TABLE_NAME表示不进行翻页的原始查询语句。ROWNUM <= 40和RN >= 21控制分页查询的每页的范围。

二、有Order by的排序写法（次优方案）

       经过测试，此方法随着查询范围的扩大，速度也会越来越慢。

SELECT *

  FROM (SELECT tt.*, ROWNUM AS rowno

          FROM (  SELECT t.*

                    FROM XXX 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;

 三、无Order by 排序的另一写法（不推荐）

    此方法随着查询数据量的扩张，速度会越来越慢

SELECT *

  FROM (SELECT ROWNUM AS rowno, t.*

          FROM k_task t

         WHERE flight_date BETWEEN TO_DATE (‘20060501‘, ‘yyyymmdd‘)

                               AND TO_DATE (‘20060731‘, ‘yyyymmdd‘)) table_alias

 WHERE table_alias.rowno <= 20 AND table_alias.rowno >= 10;

四、有order by排序的写法（不推荐）

    此方法随着查询范围的扩大，速度会越来越慢

SELECT *

  FROM (SELECT tt.*, ROWNUM AS rowno

          FROM (  SELECT *

                    FROM k_task t

                   WHERE flight_date BETWEEN TO_DATE (‘20060501‘, ‘yyyymmdd‘)

                                         AND TO_DATE (‘20060531‘, ‘yyyymmdd‘)

                ORDER BY fact_up_time, flight_no) tt) table_alias

 WHERE table_alias.rowno BETWEEN 10 AND 20;

Oracle分页查询

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原文地址：http://www.cnblogs.com/moonandstar08/p/5256145.html