Seperate Sequence for Separate Column in a Table

Question

I have following table
id,        Inv_no,         Item,          Item_Sequence
1, 132 , Processor,     
2 , 132 , RAM,     
3 , 132, DVD ROM,     
4 , 133 , Processor     ,
5, 133 , RAM,     
6 , 133 , DVD ROM     ,
7 , 953 , Processor,     
8 , 953 , Harddisk,     
9 , 953 , RAM,     
10 , 953 , DVD ROM     ,
I want to generate autosequence for "*Item_Sequence"* column, let say for processor i want pr-001, p1-002, pr-003 , and for RAM, it can be ram-001, ram-002 ......................
if i input any item it should start creating auto number for that,
If any one can help me here, Thanks in Advance
Kind Regards
Abbas
Edited by: Abbas on Apr 3, 2011 10:42 AM
Edited by: Abbas on Apr 3, 2011 10:43 AM
Edited by: Abbas on Apr 3, 2011 3:13 PM

Answer 1

Abbas wrote:
I want to generate autosequence for "*Item_Sequence"* columnFirst of all, sequence does not guarantee "no holes". If, for example, session inserting in your table rolls back or if sequence has CACHE and you restart database, seaquence will have holes. Said that, just for fun (I'd do extensive testing before using it in production):
SQL> create table inventory(
  2                         id     number,
  3                         Inv_no number,
  4                         Item   varchar2(50),
  5                         Item_Sequence number
  6                        )
  7  /
Table created.
SQL> create or replace
  2    function get_nextval(
  3                         p_seq_owner varchar2,
  4                         p_seq_name varchar2
  5                        )
  6      return number
  7      is
  8          pragma autonomous_transaction;
  9          v_cnt number;
10      begin
11          select  count(*)
12            into  v_cnt
13            from  dba_sequences
14            where sequence_owner = upper(p_seq_owner)
15              and sequence_name  = upper(p_seq_name);
16          if v_cnt = 0
17            then
18              execute immediate 'create sequence ' || p_seq_owner || '.' || p_seq_name;
19          end if;
20          execute immediate 'select ' || p_seq_owner || '.' || p_seq_name || '. nextval from dual' into v_cnt;
21          return v_cnt;
22  end;
23  /
Function created.
SQL> create or replace
  2    trigger inventory_bir
  3      before insert
  4      on inventory
  5      for each row
  6      begin
  7          :new.Item_Sequence := get_nextval('scott',replace(:new.Item,' ','_'));
  8  end;
  9  /
Trigger created.
SQL> insert into inventory(id,inv_no,item) values(1, 132 , 'Processor');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(2 , 132 , 'RAM');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(3 , 132, 'DVD ROM');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(4 , 133 , 'Processor');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(5, 133 , 'RAM');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(6 , 133 , 'DVD ROM');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(7 , 953 , 'Processor');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(8 , 953 , 'Harddisk');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(9 , 953 , 'RAM');
1 row created.
SQL> insert into inventory(id,inv_no,item) values(10 , 953 , 'DVD ROM');
1 row created.
SQL> select  *
  2    from  inventory
  3    order by item,
  4             id
  5  /
        ID     INV_NO ITEM                                               ITEM_SEQUENCE
         3        132 DVD ROM                                                        1
         6        133 DVD ROM                                                        2
        10        953 DVD ROM                                                        3
         8        953 Harddisk                                                       1
         1        132 Processor                                                      1
         4        133 Processor                                                      2
         7        953 Processor                                                      3
         2        132 RAM                                                            1
         5        133 RAM                                                            2
         9        953 RAM                                                            3
10 rows selected.
SQL> Obviously, performance will be questionable for high(er) volumes. Also, you will need to add error handler for sequence creation to ignore sequence already exists situations which can happen in multi-session environment.
SY.