Oracle 11g,,IBM pc机,winxp,双核3GHz,3G内存
1.查看表结构
SQL> desc test;
Name Type Nullable Default Comments
--------------- -------------- -------- ------- --------
ID NUMBER(8)
SER_CODE VARCHAR2(128)
SOAP_ACTION VARCHAR2(1024)
TARGET_SER_CODE VARCHAR2(100)
TARGET_SER_OPER VARCHAR2(256)
REPLY_SER_CODE VARCHAR2(100) Y
REPLY_SER_OPER VARCHAR2(1024) Y
2.获取总记录数(耗时3.297s)
SQL> select count(*) from test;
COUNT(*)
----------
638976
3.拷贝10W记录并创建新表
SQL> create table test2 as select * from test where rownum < 100000;
耗时3.469s
4.查询1000条记录
SQL> select * from test where rownum < 1000;
耗时0.966s
5.选取rownum在2-8之间的记录
SQL> select * from (select rownum rn , id from test) t where t.rn between 2 and 8;
RN ID
---------- ---------
2 302
3 1
4 2
5 30303
6 30304
7 301
8 302
耗时3.515s
SQL> select * from (select rownum rn,id from test where rownum < 8) t where t.rn between 2 and 8;
RN ID
---------- ---------
2 302
3 1
4 2
5 30303
6 30304
7 301
8 302
耗时0.056s
6.综合测试
select * from (select rownum rn , id from test where rownum <10000) t where t.rn between 2 and 10000;
耗时4.812s
select * from (select rownum rn , id from test) t where t.rn between 2 and 10000;
耗时8.172s
select * from (select rownum rn , id from test where rownum <100000) t where t.rn between 2 and 100000;
耗时47.453
select * from (select rownum rn , id from test) t where t.rn between 2 and 100000;
耗时50.703s
结论:如果使用rownum选取某一范围记录,使用子查询方式时应该加上 where rownum语句,否则会影响性能。