sql*plus问题

Question

打开后设置
set wrap off
set linesize 200
然后执行下列语句，问得到的结果中为什么没有file_id,tablespace_name列。
SQL> select file_name,file_id,tablespace_name from dba_data_files;
行将被截掉行将被截掉
FILE_NAME                                                                                                                                                                                               
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
D:\ORACLE\ORADATA\ORCL2\SYSTEM01.DBF                                                                                                                                                                    
D:\ORACLE\ORADATA\ORCL2\UNDOTBS01.DBF                                                                                                                                                                   
D:\ORACLE\ORADATA\ORCL2\CWMLITE01.DBF                                                                                                                                                                   
D:\ORACLE\ORADATA\ORCL2\DRSYS01.DBF                                                                                                                                                                     
D:\ORACLE\ORADATA\ORCL2\EXAMPLE01.DBF                                                                                                                                                                   
D:\ORACLE\ORADATA\ORCL2\INDX01.DBF                                                                                                                                                                      
D:\ORACLE\ORADATA\ORCL2\ODM01.DBF                                                                                                                                                                       
D:\ORACLE\ORADATA\ORCL2\TOOLS01.DBF                                                                                                                                                                     
D:\ORACLE\ORADATA\ORCL2\USERS01.DBF                                                                                                                                                                     
D:\ORACLE\ORADATA\ORCL2\XDB01.DBF                                                                                                                                                                       
D:\ORACLE\ORADATA\ORCL2\USER1_1.DBF                                                                                                                                                                     FILE_NAME                                                                                                                                                                                               
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
D:\ORACLE\ORADATA\ORCL2\USER1_2.DBF                                                                                                                                                                     
D:\ORACLE\ORADATA\ORCL2\OEM_REPOSITORY.DBF                                                                                                                                                              已选择13行。SQL> spool off

Answer 1

set linesize 200 
每行显示200个字符,超过长度的被截掉你再执行下面语句不就知道了吗?
select file_idfrom dba_data_files; 
select tablespace_name from dba_data_files; 

Answer 2

如下方法：
set linesize 200
col file_name format a30
select file_name,file_id,tablespace_name from dba_data_files; 

Answer 3

你的方法很有效，可为什么会出现这种情况那
==========================================
linesize 的缺省值为80，超过80的部分被截掉了

Answer 4

估算一下字段的长度，然后分别格式化 
col file_name for a30
col tablespace_name for a30