SQL 中的单列数据到多列数据的转换，以及转换后的分组统计

手上有一个供求信息网站，客户要要求对其中的企业会员每月的供求信息发布量进行统计
要求以如下形式打印：
2006-10-1 到 2006-10-31
用户    供应数   求购数   合计   详细
张山    10           20          30       >>
李四     50           3            53      >>

。。。。。

现有的供求信息表（Info）表结构如下
User             Info_ID       dateAndTime  type
WDFrog       1                   ...                       买
WDFrog       2                                             卖
WDFrog       3                                             卖
lxj                   4                                            卖
lxj                   5                                            买

则将type列拆分成  sell , buy 2列的代码如下：
   Select [Id], [user],
              case [type]
                   When '买' Then 1
               Else 0 
               End As buy,
               Case [type]
                    When '卖' Then 1
               Else 0
               End as sell      
    From info

统计求和的代码如下：

   Select [Id], [user],
           SUM(case [type]
               When '买' Then 1
               Else 0 
        End ) As buy,
           SUM(Case [type]
               When '卖' Then 1
               Else 0
               End ) as sell,
           count(info_id) as total
           
    From vi_AgentInfo

    Group by [Id],[user] Order by total DESC

最后还可以这样写，打印效果怎样？大家不妨自己去试试

Select [Id],[user],
case [type]
      When '买' Then '买'
      Else '卖'
      End As BAndS,
      count([Id]) as total

From vi_AgentInfo
Group by
 case [type]
      When '买' Then '买'
      Else '卖'
      End
      ,[Id],[user]