HELP ! 在存储过程里面无法使用变量来执行drop database 语句

[NewCenturyNewPage]

create proc proc_dropdb (@dbname varchar(20))    
as
begin
   	drop DATABASE N@dbname
end

提示错误:
消息 102，级别 15，状态 1，过程 proc_dropdb ，'@dbname' 附近有语法错误。

[水族杰纶]

--try
create proc proc_dropdb (@dbname varchar(20))    
as 
begin 
  exec('drop DATABASE '+ @dbname) 
end 

[csdyyr]

create proc proc_dropdb (@dbname varchar(20))   
as
begin
  exec('drop DATABASE'+ N@dbname)
end 

[CN_SQL]

create proc proc_dropdb (@dbname varchar(20))    
as 
begin 
	declare @s varchar(1000)
	set @s ='drop DATABASE '+@dbname 
  exec(@s)
end 

[中国风]

create proc proc_dropdb (@dbname sysname)--可定義sysname
as
begin
exec('drop DATABASE '+@dbname)--多了N
end

[bluefangxiao]

create proc proc_dropdb (@dbname varchar(20))    
as 
begin 
 declare @sql varchar(200)
 set @sql='drop database'+ @dbname
 exec(@sql)

end