ORACLE SQL优化 - ORACLE执行计划
Last login: Mon Feb 8 14:13:19 2010 from 192.168.1.249
ipnet
-bash-3.00$
-bash-3.00$ ipnet
-bash: ipnet: command not found
-bash-3.00$ su - oracle
Password:
eastcsu: incorrect password
-bash-3.00$ eastcom
-bash: eastcom: command not found
-bash-3.00$ su - oracle
Password:
[oracle@ipnet-td2 ~]$
[oracle@ipnet-td2 ~]$ sqlplus /nolog
SQL*Plus: Release 10.2.0.1.0 - Production on Mon Feb 8 14:14:08 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
SQL> su^H^H^H
SP2-0042: unknown command " - rest of line ignored.
SQL> conn ipnet/ipnet1234@ORAC^H^H^H
ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified
SQL> ^[[A^H " - rest of line ignored.
SQL> 042: unknown command "
SQL> conn ipnet/ipnet1234@ORCL
Connected.
SQL> set timn^H
SP2-0158: unknown SET option "tim"
SQL> set timing on
SQL> set autot traceonly
SQL> select v.NAME_CN from vendor v, vendordevicetype vt, devicetype t where t.name = vt.device_type_name and v.name = vt.vendor_name and t.name_cn = '防火墙';
Elapsed: 00:00:00.01
Execution Plan
----------------------------------------------------------
Plan hash value: 497066359
--------------------------------------------------------------------------------
------------------
| Id | Operation | Name | Rows | Bytes | Cost
(%CPU)| Time |
--------------------------------------------------------------------------------
------------------
| 0 | SELECT STATEMENT | | 5 | 205 | 7
(0)| 00:00:01 |
| 1 | NESTED LOOPS | | 5 | 205 | 7
(0)| 00:00:01 |
| 2 | NESTED LOOPS | | 5 | 140 | 4
(0)| 00:00:01 |
|* 3 | TABLE ACCESS FULL | DEVICETYPE | 1 | 14 | 3
(0)| 00:00:01 |
| 4 | TABLE ACCESS BY INDEX ROWID| VENDORDEVICETYPE | 5 | 70 | 1
(0)| 00:00:01 |
|* 5 | INDEX RANGE SCAN | N907275051_IDX | 5 | | 0
(0)| 00:00:01 |
| 6 | TABLE ACCESS BY INDEX ROWID | VENDOR | 1 | 13 | 1
(0)| 00:00:01 |
|* 7 | INDEX UNIQUE SCAN | NAME_4_1 | 1 | | 0
(0)| 00:00:01 |
--------------------------------------------------------------------------------
------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("T"."NAME_CN"='防火墙')
5 - access("T"."NAME"="VT"."DEVICE_TYPE_NAME")
7 - access("V"."NAME"="VT"."VENDOR_NAME")
Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
18 consistent gets
0 physical reads
0 redo size
466 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
3 rows processed
SQL>
本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/jxluoix/archive/2010/02/08/5298961.aspx
Oracle 查询 删除 重复记录
select t.*, t.rowid from test_select_delete_dump_rd t;
-- 查询表中存在重复记录的所有记录
select t.*, t.rowid from test_select_delete_dump_rd t
where
name in (
select name from test_select_delete_dump_rd
group by name
having count(name) > 1
);
-- 查询表中存在重复记录的多余记录，
-- rowid最小的记录被认为是保留记录
select * from (
select t.*, t.rowid from test_select_delete_dump_rd t
where
name in (
select name from test_select_delete_dump_rd
group by name
having count(name) > 1
)
) t2
where
t2.rowid not in (
select min(t1.rowid) from test_select_delete_dump_rd t1
group by name
having count(name) > 1
);
-- 查询表中存在重复记录的多余记录，
-- rowid最大的记录被认为是保留记录
select * from (
select t.*, t.rowid from test_select_delete_dump_rd t
where
name in (
select name from test_select_delete_dump_rd
group by name
having count(name) > 1
)
) t2
where
t2.rowid not in (
select max(t1.rowid) from test_select_delete_dump_rd t1
group by name
having count(name) > 1
);
/**
delete from test_select_delete_dump_rd
where
name in (
select name from test_select_delete_dump_rd
group by name
having count(name) > 1
)
and
rowid not in (
select min(name) from test_select_delete_dump_rd
group by name
having count(name) > 1
);
*/
dense_rank, rank：
select * from (
select deptno, ename, sal,
dense_rank() over(
partition by deptno
order by sal desc
) dr
from emp
)
where dr <= 3
order by deptno, sal desc;
select * from (
select deptno, ename, sal,
rank() over(
partition by deptno
order by sal desc
) dr
from emp
)
where dr <= 3
order by deptno, sal desc;
