use master ;

查询数据库：
select * from sysdatabases where dbid>4 ;

查询表：
SELECT * FROM SysObjects Where XType=‘U‘ ORDER BY Name

查询列：
select b.name as tableName,a.name as columnName,c.name as columnType,a.length as columnLength from syscolumns a inner join sysobjects b on a.id=b.id inner join systypes c on a.xtype=c.xtype 

WHERE a.id=OBJECT_ID(N‘[表名]‘) And c.name not like ‘sysname‘ ORDER BY colid