聚簇(Cluster)和聚簇表(Cluster Table) 
时间:2010-03-13 23:12来源:OralanDBA.CN 作者:AlanSawyer 点击:157次 
1.创建聚簇 
icmadmin@icmnlsdb> create cluster cluster_test(id int);

Cluster created.

2.创建聚簇表 
icmadmin@icmnlsdb> create table tab_cluster1(id int primary key, name1 varchar2(30)) cluster cluster_test(id);

Table created.

icmadmin@icmnlsdb> create table tab_cluster2(id int primary key, name2 varchar2(30)) cluster cluster_test(id);

Table created.

3.创建聚簇索引 
icmadmin@icmnlsdb> create index idx_cluster_test on cluster cluster_test;

Index created.

4.查看聚簇表所属的聚簇 
icmadmin@icmnlsdb> select owner,table_name,cluster_name from dba_tables where wner='icmadmin' and table_name in ('TAB_CLUSTER1','TAB_CLUSTER2');

OWNER          TABLE_NAME          CLUSTER_NAME 
-------------- ------------------- --------------- 
icmadmin            TAB_CLUSTER2        CLUSTER_TEST 
icmadmin            TAB_CLUSTER1        CLUSTER_TEST

5.初始化几行聚簇表的数据 
icmadmin@icmnlsdb> insert into TAB_CLUSTER1 values (1,'AAA'); 
icmadmin@icmnlsdb> insert into TAB_CLUSTER1 values (2,'BBB'); 
icmadmin@icmnlsdb> insert into TAB_CLUSTER1 values (3,'CCC'); 
icmadmin@icmnlsdb> insert into TAB_CLUSTER2 values (1,'AA1'); 
icmadmin@icmnlsdb> insert into TAB_CLUSTER2 values (2,'BB2'); 
icmadmin@icmnlsdb> insert into TAB_CLUSTER2 values (3,'CC3'); 
icmadmin@icmnlsdb> commit;

6.模拟truncate表TAB_CLUSTER1,可以看到报错了,聚簇中的表不允许truncate,原因很简单,聚簇在一个块上存储了多个表,必须删除聚簇表中的行来实现删除 
icmadmin@icmnlsdb> truncate table TAB_CLUSTER1; 
truncate table TAB_CLUSTER1 
               * 
ERROR at line 1: 
ORA-03292: Table to be truncated is part of a cluster

icmadmin@icmnlsdb> truncate table TAB_CLUSTER2; 
truncate table TAB_CLUSTER2 
               * 
ERROR at line 1: 
ORA-03292: Table to be truncated is part of a cluster

7.清除聚簇表第一种方法:delete方式删除

8.清除聚簇表第二种方法:通过truncate cluster的方式清除cluster中表数据 
icmadmin@icmnlsdb> truncate cluster CLUSTER_TEST;

Cluster truncated.

icmadmin@icmnlsdb> select * from TAB_CLUSTER1;

no rows selected

icmadmin@icmnlsdb> select * from TAB_CLUSTER2;

no rows selected

9.删除聚簇 
icmadmin@icmnlsdb> drop cluster cluster_test including tables;

Cluster dropped.

聚簇(Cluster)和聚簇表(Clustered Table)的优点:

1.表中的数据一起存储在簇中,连接这些表的查询就可能执行更少的I/O,改善系统性能 
2.对于经常一同查询的表可以明显的加速表的连接(Join) 
3.非常适合查询频繁的环境

聚簇(Cluster)和聚簇表(Clustered Table)的缺点:

1.因为是一类比较特殊的对象,所以增加了数据库的管理负担 
2.非常不适合更改频繁的环境 
3.如果聚簇表总是在一起查询,考虑是否可以将他们合并为一个表

聚簇(Cluster)和聚簇表(Clustered Table)的特点:

1.聚簇由多个表组成 
2.几个表共享相同的数据块 
3.一个聚簇有一个或者多个公共的列,多个表共享这些列,这样的列叫做:聚簇关键字或簇键(Cluster Key) 
4.Oracle把多个表的数据物理地存储在一起

聚簇表中插入数据之前,聚簇上需先有聚簇索引。否则会出现如下的错误: 
icmadmin@icmnlsdb> select * from tab_cluster1; 
select * from tab_cluster1 
              * 
ERROR at line 1: 
ORA-02032: clustered tables cannot be used before the cluster index is built

05-08 08:01