Question on Sequence..

Question

There is an primary key in my table which is assigned value from a sequence.
For this i first fetch the value from sequence and assign it to the column while inserting.
My question is :
How can i reset the value of the sequence in case if the insertion operation fails..
Regards
Kaustubh

Answer 1

You cannot rollback the sequence value.Don't give up so easily. Here's a very basic example of what you can do. It's not the ideal coding, but it shows the principle.
SQL> create table x (id number, x number);
Table created.
SQL>
SQL> create sequence myseq;
Sequence created.
SQL>
SQL> declare
  2    procedure insertval(x varchar2) is
  3      sq number;
  4    begin
  5      select myseq.nextval into sq from dual;
  6      dbms_output.put_line('attempting to insert sequence : '||sq);
  7      execute immediate ('insert into x values ('||sq||', '||x||')');
  8      dbms_output.put_line('success');
  9    exception
10      when others then
11        dbms_output.put_line('failure');
12        execute immediate ('alter sequence myseq increment by -1');
13        declare
14          dummy number;
15        begin
16          execute immediate ('select myseq.nextval from dual') into dummy;
17          dbms_output.put_line('sequence rolled back by 1 to '||dummy);
18        end;
19        execute immediate ('alter sequence myseq increment by 1');
20    end;
21  begin
22    insertval('1');
23    insertval('2');
24    insertval('a');
25    insertval('3');
26    insertval('4');
27  end;
28  /
attempting to insert sequence : 1
success
attempting to insert sequence : 2
success
attempting to insert sequence : 3
failure
sequence rolled back by 1 to 2
attempting to insert sequence : 3
success
attempting to insert sequence : 4
success
PL/SQL procedure successfully completed.
SQL>
SQL> select * from x;
        ID          X
         1          1
         2          2
         3          3
         4          4
SQL>