SQL 获取一些实用信息的方法

1。获取数据库列表

针对SQL2005，对于所有的数据库，都存在系统表“sysdatabases”中，获取起来比较简单

select * from sysdatabases where name not in ('master','model','msdb','tempdb')

where后面的语句是为了不获取SQL的系统数据库，大家可以不加条件，就能获取所有数据库了。

2。获取指定数据库中的所有数据表/视图的列表

针对SQL2005，所有表/视图，都存储在“sysobjects”系统表中，而所有表的字段信息，则主要存储在“syscolumns”系统表中，另外，还有一个重要的系统表“systypes”主要存储数据库中系统定义和用户自定义的数据类型。

获取所有表的名字和每个表的字段数目：

string
SqlStr_Tbl = @"select sysobjects.name ,count(*) as ColsCount from
syscolumns,sysobjects,systypes where syscolumns.id=sysobjects.id and
syscolumns.xtype=systypes.xtype and sysobjects.type='U' and
systypes.name <>'_default_' and systypes.name<>'sysname'
group by sysobjects.name order by sysobjects.name";

获取所有视图的名字和每个视图的字段数目：

string
SqlStr_Vw = @"select sysobjects.name ,count(*) as ColsCount from
syscolumns,sysobjects,systypes where syscolumns.id=sysobjects.id and
syscolumns.xtype=systypes.xtype and sysobjects.type='V' and
systypes.name <>'_default_' and systypes.name<>'sysname'
group by sysobjects.name order by sysobjects.name";

3。获取指定表的所有字段属性

下面的语句中，只要代入不同的表/视图名，就可以获取该表的所有字段名字、字段长度、字段类型、字段说明、字段是否允许为空、是否主键、是否自增长字段等。

string
SqlStr = @"select syscolumns.name as ColName ,systypes.name as
ColTypeName , syscolumns.length, sys.extended_properties.value as Mark
,syscolumns.isnullable as AllowNull ,IsPK = Case when exists ( select 1
from sysobjects inner join sysindexes on sysindexes.name =
sysobjects.name inner join sysindexkeys on sysindexes.id =
sysindexkeys.id and sysindexes.indid = sysindexkeys.indid where
xtype='PK' and parent_obj = syscolumns.id and sysindexkeys.colid =
syscolumns.colid ) then 1 else 0 end ,IsIdentity = Case
syscolumns.status when 128 then 1 else 0 end from syscolumns inner join
systypes on ( syscolumns.xtype = systypes.xtype and systypes.name
<>'_default_' and systypes.name<>'sysname' ) left outer join
sys.extended_properties on (
sys.extended_properties.major_id=syscolumns.id and
minor_id=syscolumns.colid ) where syscolumns.id = (select id from
sysobjects where name='" + TableName + @"') order by syscolumns.colid ";