1.獲取所有數據庫名:
SELECT Name FROM Master..SysDatabases ORDER BY Name
2.獲取所有表名:
SELECT Name FROM DatabaseName..SysObjects Where XType='U' ORDER BY Name
XType='U':表示所有用戶表;
XType='S':表示所有系統表;
3.獲取所有字段名:
SELECT Name FROM SysColumns WHERE id=Object_Id('TableName')

SELECT
    表名 = case when a.colorder = 1 then d.name else '' end,
    表說明 = case when a.colorder = 1 then isnull(f.value, '') else '' end,
    字段序號 = a.colorder,
    字段名 = a.name,
    標識 = case when COLUMNPROPERTY(a.id, a.name, 'IsIdentity')= 1 then '√'else '' end,
    主鍵 = case when exists(SELECT 1 FROM sysobjects where xtype = 'PK' and parent_obj = a.id and name in (
               SELECT name FROM sysindexes WHERE indid in(SELECT indid FROM sysindexkeys WHERE id = a.id AND colid = a.colid))) then '√' else '' end,
    類型 = b.name,
    占用字節數 = a.length,
    長度 = COLUMNPROPERTY(a.id, a.name, 'PRECISION'),
    小數位數 = isnull(COLUMNPROPERTY(a.id, a.name, 'Scale'), 0),
    允許空 = case when a.isnullable = 1 then '√'else '' end,
    默認值 = isnull(e.text, ''),
    字段說明 = isnull(g.[value], '')
FROM
    syscolumns a
left join
    systypes b
on
    a.xusertype = b.xusertype
inner join
    sysobjects d
on
    a.id = d.id  and d.xtype = 'U' and d.name <> 'dtproperties'
left join
    syscomments e
on
    a.cdefault = e.id
left join
sys.extended_properties g
on
    a.id = G.major_id and a.colid = g.minor_id
left join
sys.extended_properties f
on
    d.id = f.major_id and f.minor_id = 0
where
    d.name = 'tablename'--如果只查詢指定表,加上此where條件，tablename是要查詢的表名；去除where條件查詢所有的表信息
order by
    a.id,a.colorder