--一般用這個就行了 

 SELECT
  B.COLUMN_Name AS 字段名,
  B.DATA_TYPE AS 字段類型,
  case when c.column_name is not null then 'P' end 主鍵,
  B.DATA_LENGTH AS 字段長度,
  case when B.NULLABLE='N' then '否' else '是' end AS 是否為空,
  decode(B.NULLABLE,'N',
         decode(B.DATA_TYPE,'NUMBER','0','DATE','SYSDATE')
         ) AS 字段默認(rèn)值,
  Comments AS 字段說明
   FROM USER_COL_COMMENTS A,
 USER_TAB_COLUMNS B ,all_ind_columns c
where A.table_name = B.TABLE_NAME
  AND A.column_name = B.COLUMN_NAME
  and a.table_name=c.table_name(+)
  and a.column_name=c.column_name(+)
  and B.TABLE_NAME='USERS'
order by b.table_name,b.COLUMN_ID

 

 

select t.COLUMN_NAME as 字段名,
       t.DATA_TYPE as 字段類型,
       t.DATA_LENGTH as 字段長度,
       t.DATA_PRECISION as 數(shù)據(jù)精度,
       t.DATA_SCALE as 小數(shù)位,
       case when t.NULLABLE='Y' then '是' else '否' end as 是否允許為空,
       c.COMMENTS as 備注  
  from user_tab_columns t, user_col_comments c
 where t.table_name = c.table_name
   and t.column_name = c.column_name
   and t.table_name = 'USERS'
   order by t.COLUMN_ID ;