SQL查询所有表，字段名，主键，类型，长度，小数位数，允许空，默认值，字段说明

SELECT 
       (case when a.colorder=1 then d.name else '' end)表名,
       a.colorder 字段序号,
       a.name 字段名,
       (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) 标识,
       (case when (SELECT count(*)
       FROM sysobjects
       WHERE (name in
                 (SELECT name
                FROM sysindexes
                WHERE (id = a.id) AND (indid in
                          (SELECT indid
                         FROM sysindexkeys
                         WHERE (id = a.id) AND (colid in
                                   (SELECT colid
                                  FROM syscolumns
                                  WHERE (id = a.id) AND (name = a.name))))))) AND
              (xtype = 'PK'))>0 then '√' else '' end) 主键,
       b.name 类型,
       a.length 占用字节数,
       COLUMNPROPERTY(a.id,a.name,'PRECISION') as 长度,
       isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as 小数位数,
       (case when a.isnullable=1 then '√'else '' end) 允许空,
       isnull(e.text,'') 默认值,
       isnull(g.[value],'') AS 字段说明    
FROM  syscolumns  a left join systypes b 
on  a.xtype=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  
order by a.id,a.colorder