sql server中查找特定类别的列的写法

select a.name, o.name AS TableName, o.type, a.id, o.object_id, o.schema_id
  FROM sys.syscolumns AS a INNER JOIN sys.systypes AS b ON a.xtype = b.xtype
  AND b.name = nvarchar
   INNER JOIN
  sys.objects AS o ON a.id = o.object_id
  WHERE (o.type = u)
 AND (o.schema_id = 1)