reset number order in db2sql - sql

Question

how to reset the existing data order number ? i tried alter table tb_shk_user alter column autonum restart with 1, it works only for new data insert the number will start from 1 the number but will duplicated with existing 1.
autonum column attribute
AUTONUM INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1) primary key

Answer 1

or this :
--Save data of your table into temporary table
create table tmptable as
(
select * from tb_shk_user
)
with data;
--Remove all rows into your table
delete from tb_shk_user ;
--Insert into your table all rows with renumber for autonum, be carefull all columns mus be in select except autonum
insert into tb_shk_user overriding system value
select rownumber() over(order by autonum) as newautonum, username, mobilno
from tmptable;
-- Reposition of autoincrement on max + 1
-- Example if 47896 is the max + 1 of autonum after preceding insert
alter table tb_shk_user alter column autonum restart with 47896;

Answer 2

I suppose you want restart for have a good series of id, then you cando it
--Temprary table with key autonum and new num ordered
create table tmptable as (
select autonum, rownumber() over(order by autonum) as newautonum
from tb_shk_user
) with data;
--Update your table with new num
update tb_shk_user f1 overriding system value
set f1.autonum=
(
select f2.newautonum from tmptable f2
where f1.autonum=f2.autonum
)
where exists
(
select * from tmptable f2
where f1.autonum=f2.autonum
);
-- Reposition of autoincrement on max + 1
-- Example if 47896 is the max + 1 of autonum after preceding update
alter table tb_shk_user alter column autonum restart with 47896;