Index-Organized Tables(IOT)不同于一般的heap table,它将数据按照primary key的顺序组织存储,
对普通表:索引和数据是分开存放的,对IOT数据就是索引了;
PCTTHRESHOLD 在数据块中 超过此百分比部分将存储到overflow指定存储空间
OVERFLOW 指定的超过pctthreshold部分的存储空间
INCLUDING 指定列后的数据将存储到overflow data segment;
SQL> create table test(empno number(4) primary key,
2 ename varchar2(10),job varchar2(9),
3 deptno number(2))
4 organization index
5 pctthreshold 20
6 including ename
7 overflow tablespace example;
Table created.
SQL> select index_name, index_type
2 from user_indexes
3 where table_name='TEST';
INDEX_NAME INDEX_TYPE
------------------------------ ---------------------------
SYS_IOT_TOP_30429 IOT - TOP
SQL> alter table test initrans 3 overflow initrans 5;
Table altered.
SQL> alter table test pctthreshold 15 including job;
Table altered.
SQL> desc test;
Name Null? Type
----------------------------------------- -------- ----------------------------
EMPNO NOT NULL NUMBER(4)
ENAME VARCHAR2(10)
JOB VARCHAR2(9)
DEPTNO NUMBER(2)
SQL> insert into test
2 values(1002,'aaaa','dba',10);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from test;
EMPNO ENAME JOB DEPTNO
---------- ---------- --------- ----------
1002 aaaa dba 10
SQL> alter table test move online;
Table altered.
SQL>
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