全表扫描分页

SQL> set linesize 200
SQL> set pagesize 200
SQL> alter session set statistics_level=all; 

Session altered.

SQL> select  *  from ( select rownum as rn ,a.* from ( select
*	from page a   )a where rownum<=20 ) a  where rn>=0  2  ;

20 rows selected.

SQL> select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------
SQL_ID	axby03b75am6v, child number 0
-------------------------------------
select	*  from ( select rownum as rn ,a.* from ( select * from page a
 )a where rownum<=20 ) a  where rn>=0

Plan hash value: 2590430161

--------------------------------------------------------------------------------------
| Id  | Operation	    | Name | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |	   |	  1 |	     |	   20 |00:00:00.01 |	   6 |
|*  1 |  VIEW		    |	   |	  1 |	  20 |	   20 |00:00:00.01 |	   6 |
|*  2 |   COUNT STOPKEY     |	   |	  1 |	     |	   20 |00:00:00.01 |	   6 |
|   3 |    TABLE ACCESS FULL| PAGE |	  1 |	  20 |	   20 |00:00:00.01 |	   6 |
--------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN">=0)
   2 - filter(ROWNUM<=20)


22 rows selected.


取第2页:

SQL> select  *  from ( select rownum as rn ,a.* from ( select
*	from page a   )a where rownum<=40 ) a  where rn>=21  2  ;


20 rows selected.

SQL> select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------
SQL_ID	crwugd6xrr3nb, child number 0
-------------------------------------
select	*  from ( select rownum as rn ,a.* from ( select * from page a
 )a where rownum<=40 ) a  where rn>=21

Plan hash value: 2590430161

--------------------------------------------------------------------------------------
| Id  | Operation	    | Name | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |	   |	  1 |	     |	   20 |00:00:00.01 |	   6 |
|*  1 |  VIEW		    |	   |	  1 |	  40 |	   20 |00:00:00.01 |	   6 |
|*  2 |   COUNT STOPKEY     |	   |	  1 |	     |	   40 |00:00:00.01 |	   6 |
|   3 |    TABLE ACCESS FULL| PAGE |	  1 |	  40 |	   40 |00:00:00.01 |	   6 |
--------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN">=21)
   2 - filter(ROWNUM<=40)


22 rows selected.