Oracle常用命令_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
　　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