250.表结构（已用数据的最大长度）

create table #t(id int,colid int,datalen bigint)
exec sp_msforeachtable @command1=N'
declare @s1 nvarchar(4000),@s2 nvarchar(4000)
select @s1='''',@s2=''''
select @s1=@s1+'' union all select ''
		+rtrim(c.id)+'',''
		+rtrim(c.colid)+'',''
		+quotename(c.colid)+'' from #'',
	@s2=@s2+N'',''+quotename(c.colid)+''=max(''+case
		when t.name in(''sql_variant'',''image'',''money'')
			or t.name like ''%text'' 
			or t.name like ''%binary''
		then ''datalength'' else ''len'' end
		+''(''+quotename(c.name)+''))''	
from syscolumns c,systypes t
where c.xusertype=t.xusertype
	and object_id(''?'')=c.id
order by colid
select @s1=stuff(@s1,1,10,''''),
	@s2=stuff(@s2,1,1,'''')
exec(''select ''+@s2+'' into # from ? insert #t ''+@s1)'
--,@whereand=' and o.name=''要查询的表'''  --如果只查询指定表,加上此条件

SELECT 
	表名=case when a.colorder=1 then d.name else '' end,
	表说明=case when a.colorder=1 then isnull(f.value,'') else '' end,
	字段序号=a.colorder,
	字段名=a.name,
	标识=case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end,
	主键=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,
	类型=b.name,
	占用字节数=a.length,
	长度=COLUMNPROPERTY(a.id,a.name,'PRECISION'),
	已有数据的最大长度=data.datalen,
	小数位数=isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0),
	允许空=case when a.isnullable=1 then '√'else '' end,
	默认值=isnull(e.text,''),
	字段说明=isnull(g.[value],'')
FROM syscolumns a
	inner join #t data on a.id=data.id and a.colid=data.colid
	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 sysproperties g on a.id=g.id and a.colid=g.smallid  
	left join sysproperties f on d.id=f.id and f.smallid=0
--where d.name='要查询的表'    --如果只查询指定表,加上此条件
order by a.id,a.colorder
drop table #t