Oracle 删除表中的列
CONN SCOTT/TIGER DROP TABLE T1; create table t1 as select * from emp; insert into t1 select * from t1; / / --到6000行，构造一个实验用大表T1。 COMMIT;
select EXTENT_ID,FILE_ID,BLOCK_ID,BLOCKS from dba_extents where SEGMENT_NAME='T1' AND OWNER='SCOTT';
--删除指定的一列 alter table t1 drop column hiredate; alter table t1 move tablespace users; select EXTENT_ID,FILE_ID,BLOCK_ID,BLOCKS from dba_extents where SEGMENT_NAME='T1' AND OWNER='SCOTT';
--禁用多列 alter table t1 set unused column comm; alter table t1 set unused column sal; alter table t1 set unused column mgr; --验证是否释放空间 alter table t1 move tablespace users; select EXTENT_ID,FILE_ID,BLOCK_ID,BLOCKS from dba_extent