SELECT OWNER,SYNONYM_NAME,TABLE_OWNER,TABLE_NAME from all_SYNONYMs where SYNONYM_NAME ='同义词名1' and OWNER = 'OPS$用户名1'；
查找用户1的同义词1连接在哪个用户的哪个表上
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create table 表名;   drop table 表名;
create synonym 同义词名1 for OPS$用户名1.表名；
drop synonym 同义词名;
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SELECT table_name ,INDEX_NAME,COLUMN_POSITION,column_name from user_ind_columns where table_name='表名'；
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exp userid= / file =WTB1111.dmp TABLES=\(表1，表2，表3，表4\)
imp userid= / file =WTB1111.dmp TABLES=\(表1，表2，表3，表4\)IGNORE =y CONSTRAINTS =n
exp 将当前用户的表1，表2，表3，表4打成WTB1111.dmp, imp 把WTB1111.dmp导入到当前用户，包括表结构，主KEY，数据。。
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alter table 表1 add(字段1 char(1),字段2 number(8));
update 表1 set 字段1=' ',字段2=0;
alter table 表1 modify(字段1 char(1) NOT NULL,字段2 number(8) NOT NULL);
insert into 表1 values ('eee',1000,'bbbb');
insert into 表1 select *from 表2;
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set linesize 100;
set trimspool on;
set feedback off;
spool /usr3/gjj/print_into.txt  //将屏幕显示内容打印到print_into.txt中
spool off;
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select g.instance_name,D.tablespace_name name,D.file_name datafile,d.bytes/1024/1024 "FREE(MB)",ROUND((e.used_bytes/d.bytes)*100,2)"%USED"
from dba_data_files d,
(select file_id,sum(decode(bytes,null,0,bytes))used_bytes from dba_extents froup by file_id)e,
(select sum(bytes) free_bytes,file_id from dba_free_space group by file_id)f,v$instance g
where d.file_id = e.file_id(+) and d.file_id = f.file_id(+)order by d.tablespace_name