create procedure AA
as 
  begin
    declare @s varchar(1000)
    set @s = 'select '
    declare @_i int
    declare @_len int
    select @_len=max(len(cityname)) from dbo.T_city  
    set @_i=1  
    while @_i <= @_len
      begin
        set @s = @s + ' substring(cityname , ' + ltrim(@_i) + ' , ) ,'
        set @_i=@_i+1
      end
    set @s = substring(@s , 1 , len(@s) - 1) + ' from dbo.T_city'
    exec cit_name
  end

------解决方案--------------------

--如果你的不够@_len怎么办?,也许下面的好点.
SQL code
create procedure AA
as 
  begin
    declare @s varchar(1000)
    set @s = 'select '
    declare @_i int
    declare @_len int
    select @_len=max(len(cityname)) from dbo.T_city  
    set @_i=1  
    while @_i <= @_len
      begin
        set @s = @s + ' substring(cityname , ' + ltrim(@_i) + ' , ) ,'
        set @_i=@_i+1
      end
    set @s = substring(@s , 1 , len(@s) - 1) + ' from dbo.T_city where len(cityname) >= ' + ltrim(@_len)
    exec cit_name
  end