在文章的最后看一下ORDER BY STOPKEY和ORDER BY在翻页查询的最后几页的性能差异：

SQL> CREATE TABLE T AS SELECT A.* FROM DBA_OBJECTS A, DBA_USERS B, TAB;

表已创建。

SQL> SELECT COUNT(*) FROM T;

COUNT(*)
----------
458064

SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(USER, 'T')

PL/SQL 过程已成功完成。

SQL> SET AUTOT TRACE
SQL> SET TIMING ON
SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T ORDER BY TIMESTAMP
8 )
9 WHERE ROWNUM <= 20
10 )
11 WHERE RN >= 11;

已选择10行。

已用时间: 00: 00: 00.03

Execution Plan
----------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=13888 Card=20 Bytes=1840)
1 0 VIEW (Cost=13888 Card=20 Bytes=1840)
2 1 COUNT (STOPKEY)
3 2 VIEW (Cost=13888 Card=458064 Bytes=36187056)
4 3 SORT (ORDER BY STOPKEY) (Cost=13888 Card=458064 Bytes=18780624)
5 4 TABLE ACCESS (FULL) OF 'T' (Cost=537 Card=458064 Bytes=18780624)

Statistics
----------------------
0 recursive calls
0 db block gets
5579 consistent gets
0 physical reads
0 redo size
694 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
10 rows processed

SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T ORDER BY TIMESTAMP
8 )
9 )
10 WHERE RN BETWEEN 11 AND 20;

已选择10行。

已用时间: 00: 00: 09.05

Execution Plan
----------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=13888 Card=458064 Bytes=42141888)
1 0 VIEW (Cost=13888 Card=458064 Bytes=42141888)
2 1 COUNT
3 2 VIEW (Cost=13888 Card=458064 Bytes=36187056)
4 3 SORT (ORDER BY) (Cost=13888 Card=458064 Bytes=18780624)
5 4 TABLE ACCESS (FULL) OF 'T' (Cost=537 Card=458064 Bytes=18780624)

Statistics
----------------------
0 recursive calls
41 db block gets
5579 consistent gets
7935 physical reads
0 redo size
689 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
1 sorts (disk)
10 rows processed

对于翻页查询的前几页，采用ORDER BY STOPKEY的方式比ORDER BY性能上有很大的优势，那么对于分页查询的最后几页，ORDER BY STOPKEY是否和其他分页查询技术一样，性能比普通方式还要低很多：

SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T ORDER BY TIMESTAMP
8 )
9