SQL最大值加1

CREATE   FUNCTION GetMaxbhInc (@bh varchar(50))  
    RETURNS varchar(50) 
AS  
BEGIN 
    declare @return varchar(50),@i int,@len int,@v int,@vs varchar(10)
    
    set @bh=isnull(@bh,'00')

    set @len=len(@bh)
    
    set @i=patindex('%[0-9]%',@bh)
    if @i=0 
    begin
        set @return=@bh+'1'
    end
    else    
    begin
        set @len=@len-@i+1
        set @v=cast(right(@bh,@len) as int )+1
        set @vs=cast(@v as varchar)
        if @len<len(@vs)
            set @len=len(@vs)
        
        set @return=left(@bh,@i-1)+right('0000000000000000'+@vs,@len)
    end


    return  @return
END