ORACLE 表管理

最新推荐文章于 2023-05-18 08:39:47 发布

原创最新推荐文章于 2023-05-18 08:39:47 发布 · 1k 阅读

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#oracle #table #constraints #integer #sql #subquery

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本文围绕Oracle数据库展开，介绍了表的多种操作。包括创建表、复制现有表、创建临时表，还涉及表的存储和块利用率参数修改、手动分配区、移动表空间、释放未使用空间、截断表、删除表、删除列以及标记列未使用等操作。

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1.create a table
sql> create table table_name (column datatype,column datatype]....)
sql> tablespace tablespace_name [pctfree integer] [pctused integer]
sql> [initrans integer] [maxtrans integer]
sql> storage(initial 200k next 200k pctincrease 0 maxextents 50)
sql> [logging|nologging] [cache|nocache]

2.copy an existing table
sql> create table table_name [logging|nologging] as subquery

3.create temporary table
sql> create global temporary table xay_temp as select * from xay;
on commit preserve rows/on commit delete rows

4.pctfree = (average row size - initial row size) *100 /average row size
pctused = 100-pctfree- (average row size*100/available data space)

5.change storage and block utilization parameter
sql> alter table table_name pctfree=30 pctused=50 storage(next 500k
sql> minextents 2 maxextents 100);

6.manually allocating extents
sql> alter table table_name allocate extent(size 500k datafile 'c:/oracle/data.dbf');

7.move tablespace
sql> alter table employee move tablespace users;

8.deallocate of unused space
sql> alter table table_name deallocate unused [keep integer]

9.truncate a table
sql> truncate table table_name;

10.drop a table
sql> drop table table_name [cascade constraints];

11.drop a column
sql> alter table table_name drop column comments cascade constraints checkpoint 1000;
alter table table_name drop columns continue;

12.mark a column as unused
sql> alter table table_name set unused column comments cascade constraints;
alter table table_name drop unused columns checkpoint 1000;
alter table orders drop columns continue checkpoint 1000
data_dictionary : dba_unused_col_tabs