在case when中实现变量赋值
我想让orderid等于10253时,让@i的值加1,可是要报错: 
 use   northwind 
 go 
 declare   @i   int 
 set   @i=1; 
 select   case   orderid   when   10253   then   @i=@i+1   else   1   end   from   orders 
 请问用select语句怎么实现orderid等于10253时,让@i的值加1? 
 谢谢
------解决方案--------------------select @i = case orderid when 10253 then @i+1 else 1 end from orders 
------解决方案--------------------use northwind 
 go 
 declare @i int 
 set @i = 1 
 select @i = @i + 1 from orders where orderid = 10253