一、oracle
1、獲取當前oracle資料庫中的所有表
select table_name from user_tables
2、查詢某個表中的欄位名稱、型別、精度、長度、是否為空
select column_name,data_type,data_precision,data_scale,nullable
from user_tab_columns
where table_name ='yourtablename'
3、查詢某個表中的主鍵欄位名
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、查詢某個表中的外來鍵欄位名稱、所引用表名、所應用欄位名
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、如何從oracle中取得表的注釋
user_tab_comments;表注釋
user_col_comments;表字段注釋
以上兩個只能獲取自己使用者的表的注釋資訊，如果要訪問自己
能夠訪問的其他使用者的表，則需要使用：
all_tab_comments;表注釋
all_col_comments;表字段注釋
當然，如果有dba許可權，則可以使用
dba_tab_comments;表注釋
dba_col_comments;表字段注釋
dba*和all*最好指定owner條件。user*沒有該欄位
user_tab_comments;表注釋
user_col_comments;表字段注釋
二、sqlserver
1、讀取庫中的所有表名
select name from sysobjects where xtype='u'
2、字段
select c.name,t.name,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、主鍵（參考sqlserver系統儲存過程sp_pkeys）
select column_name = convert(sysname,c.name)
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 (c.name = index_col ('[yourtablename]', i.indid, 1) or
c.name = index_col ('[yourtablename]', i.indid, 2) or
c.name = index_col ('[yourtablename]', i.indid, 3) or
c.name = index_col ('[yourtablename]', i.indid, 4) or
c.name = index_col ('[yourtablename]', i.indid, 5) or
c.name = index_col ('[yourtablename]', i.indid, 6) or
c.name = index_col ('[yourtablename]', i.indid, 7) or
c.name = index_col ('[yourtablename]', i.indid, 8) or
c.name = index_col ('[yourtablename]', i.indid, 9) or
c.name = index_col ('[yourtablename]', i.indid, 10) or
c.name = index_col ('[yourtablename]', i.indid, 11) or
c.name = index_col ('[yourtablename]', i.indid, 12) or
c.name = index_col ('[yourtablename]', i.indid, 13) or
c.name = index_col ('[yourtablename]', i.indid, 14) or
c.name = index_col ('[yourtablename]', i.indid, 15) or
c.name = index_col ('[yourtablename]', i.indid, 16)
) 4、外來鍵
select t1.name,t2.rtablename,t2.name
from
(select col.name, f.constid as temp
from syscolumns col,sysforeignkeys f
where f.fkeyid=col.id
and f.fkey=col.colid
and f.constid in
( select distinct(id)
from sysobjects
where object_name(parent_obj)='yourtablename'
and xtype='f'
) ) as t1 ,
(select object_name(f.rkeyid) as rtablename,col.name, f.constid as temp
from syscolumns col,sysforeignkeys f
where f.rkeyid=col.id
and f.rkey=col.colid
and f.constid in
( select distinct(id)
from sysobjects
where object_name(parent_obj)='yourtablename'
and xtype='f'
) ) as t2
where t1.temp=t2.temp
三、access
1、所有表清單
conn.open();
dt= conn.getoledbschematable(oledbschemaguid.tables, new object );
2、表結構
conn.open();
dtcolumnsinfo = conn.getoledbschematable(oledbschemaguid.columns, new object );
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