conn scott/tiger
DROP TABLE EMP1 PURGE;
CREATE TABLE EMP1 AS SELECT * FROM EMP;
alter table emp1 enable row movement;
-- 启动回缩特性
insert into emp1 select * from emp1;
/
/
commit;
-- 增加到14000行
-- 分析表的结构
analyze table emp1 compute statistics;
select NUM_ROWS,BLOCKS,EMPTY_BLOCKS,AVG_SPACE from tabs where table_name='EMP1';
-- 查询高水位
delete emp1 where deptno=30;
commit;
-- 删除一半的数据
analyze table emp1 compute statistics;
-- 分析表的结构
select NUM_ROWS,BLOCKS,EMPTY_BLOCKS,AVG_SPACE from tabs where table_name='EMP1';
-- 查询高水位
SELECT DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) BLOCK#,COUNT(*) FROM EMP1
GROUP BY DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID);
-- 查询块内行的分布
SELECT EXTENT_ID,BLOCK_ID,BLOCKS FROM DBA_EXTENTS WHERE SEGMENT_NAME='EMP1';
-- 将数据挪动到表的前端，但不回缩高水位
alter table EMP1 shrink space compact;
-- 回缩高水位
alter table EMP1 shrink space ;
analyze table emp1 compute statistics;
select NUM_ROWS,BLOCKS,EMPTY_BLOCKS,AVG_SPACE from tabs where table_name='EMP1';
该特性和压缩的特性冲突。