个表中的字段名称、类型、精度、长度、是否为空
select COLUMN_NAME,DATA_TYPE,DATA_PRECISION,DATA_SCALE,NULLABLE
from user_tab_columns
where table_name ='YourTableName'
3、查询某个表中的主键字段名
select col.column_name
from user_constraints con, user_cons_columns col
where con.constraint_name = col.constraint_name
and con.constraint_type='P'
and col.table_name = 'YourTableName'
4、查询某个表中的外键字段名称、所引用表名、所应用字段名
select distinct(col.column_name),r.table_name,r.column_name
from
user_constraints con,
user_cons_columns col,
(select t2.table_name,t2.column_name,t1.r_constraint_name
from user_constraints t1,user_cons_columns t2
where t1.r_constraint_name=t2.constraint_name
and t1.table_name='YourTableName'
) r
where con.constraint_name=col.constraint_name
and con.r_constraint_name=r.r_constraint_name
and con.table_name='YourTableName'
5、如何从Oracle中取得表的注释

user_tab_comments;表注释

user_col_comments;表字段注释

　 以上两个只能获取自己用户的表的注释信息，如果要访问自己

能够访问的其他用户的表，则需要使用：

all_tab_comments;表注释

all_col_comments;表字段注释

　 当然，如果有DBA权限，则可以使用

dba_tab_comments;表注释

dba_col_comments;表字段注释

　 dba*和all*最好指定owner条件。user*没有该字段

user_tab_comments;表注释

user_col_comments;表字段注释


二、SQLServer

1、读取库中的所有表名

　　select name from sysobjects where xtype='u'

2、字段
SELECT ,,c.xprec,c.xscale,c.isnullable
FROM systypes t,syscolumns c
WHERE t.xtype=c.xtype
AND c.id = (SELECT id FROM sysobjects WHERE name='YourTableName')
ORDER BY c.colid
3、主键（参考SqlServer系统存储过程sp_pkeys）
select COLUMN_NAME = convert(sysname,)
from
sysindexes i, syscolumns c, sysobjects o
where o.id = object_id('[YourTableName]')
and o.id = c.id
and o.id = i.id
and (i.status & 0x800) = 0x800
and ( = index_col ('[YourTableName]', i.indid, 1) or
= index_col ('[YourTableName]', i.indid, 2) or
= index_col ('[YourTableName]', i.indid, 3) or
http://doc.guandang.
net = index_col ('[YourTableName]', i.indid, 4) or
= index_col ('[YourTableName]', i.indid, 5) or