Question

I want to make some inserts into a table, using some data from powerbuilder. I am a little lost when it comes to using SQL sequences to increment the last known ID.

I know how to find the max ID, but how can I use a sequence to make sure that every new INSERT increments the ID by 1?

So far all I have is how to find my max id:

SELECT MAX(id)
FROM table_name;

EDIT
I am using Oracle for my database

Thanks.

Answer 1

In oracle, to get the next value in the sequence, you use .nextval.

Example :

select my_sequence.nextval from dual;

When you are importing data and let’s say ids till 10000 have been used up already, you could alter your sequence to increment by that number. Since this is DDL, you might have to use Dynamic SQL.

declare
  l_current_max_value number;
  l_dummy number
begin
  select max(id)
    into l_current_max_value 
    from my_table;

  for i in 1..l_current_max_value loop
    l_dummy := l_current_max_value.nextval; --bouncing the sequence, 
                                            --another option is to recreate it.
  end loop; 

end;
/

NOTE: THis is asuming your current sequence isn’t used at all. If you are importing data into an existing table with data, it will be more work along the same lines and you need to think about common Ids in both tables.

EDIT : “how do I assign the current_max_number to the my_sequence”

Once all the importing is done, you can get the ids using .nextval. Eg.

create or replace procedure new_product(
  i_sku in number,
  i_name in varchar2(100)
)
as
begin
  insert into new_product (id, sku, name)
  values (product_seq.nextval, i_sku, i_name);

  commit;
end;
/

or you can get it into a variable for any further processing..

declare
 l_next_id number;
begin
 select my_sequence.nextval
   into l_next_id
   from dual;
 --further processing
end;
/