Issue in setting unique ID in Domino designer

Question

I am new to Domino designer and lotus script,

following my second question,

I have some issue in setting unique ID (for id field in form).

My formula for Id field value :

T_List:=@DbColumn("" : "NoCache"; "Local"; "DBintro";"testview"; 1); @If(@IsNewDoc & @Elements(T_List)=0;1;@IsNewDoc & !@IsError(T_List);@Subset(T_List;1) + 1;id)

I'm having DB in local (nothing shared).

referred this link an Answer by AndrewB

Server : Local

DBname : DBintro

view name : testview id - field in the form (which is set when required to save in DB)

Error I'm getting

Field id ! does not exist

Please help me to get out of this.. Thanks

EDIT :1 Updated code

T_List:=@DbColumn("" : "NoCache"; "Local"; "DBintro";"testview"; 1);
T_List:=@Sort(T_List; [DESCENDING]);
@if(@Iserror(T_List);
  1;
  @Subset(T_List;1)+1
);

Answer 1

Set type of field "testid" to "Number"
Change formula to

_List:=@DbColumn("" : "NoCache"; ""; "testview"; 1);
@If(    @IsError(_List);
            1;
        _List = "";
            1;
            @Subset(_List; 1) + 1
)

Set column sort to "Descending"