oracle 表操作

表

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 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

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