Inserting to a table using same table and master table

Question

[code]
I have a table  test_master where I have stored the status of the individual claims  ; the status would be changed quarterly basis.
I have another table test_detail which will store status chages on each quarter.The curr_status column will store the status from test_master; and  prev_status will be the curr_status for the previous  trans_id from test_detail table itself
create table test_master( claim_id number,
                        status varchar2(10));
insert into  test_main VALUES (100, 'L1');                
insert into  test_main VALUES (101, 'L2');   ---- first quarter data.. it will be purged at the begining of second quarter
insert into  test_main VALUES (102, 'L1');
insert into  test_main VALUES (103, 'L3');
insert into  test_main VALUES (100,  'L2');
insert into  test_main VALUES (101,  'L2');    ---- second quarter data.. it will be purged at the begining of third quarter  
insert into  test_main VALUES (102,  'L1');
insert into  test_main VALUES (103,  'L4');
insert into  test_main VALUES (100,  'L4');
insert into  test_main VALUES (101,  'L5');    ---- third quarter data.. it will be purged at the begining of fourth quarter  
insert into  test_main VALUES (102,  'L6');
insert into  test_main VALUES (103,  'L7');
create table test_detail( trans_id number,
                          claim_id number,
                          prev_status varchar(20),
                          curr_status varchar2(21
prev_status =  curr_status of  the previous id for same claim_id s
curr_status =  status from TEST_MASTER
how to write an insert statement to insert records in TEST_DETAIL to have below expected data?
id     claim_id       PREV_STATUS      CURR_STATUS
1          100                               null               L1    ---prev_status will be null for the first run
1          101                               null               L2
1          102                               null               L1
1          103                               null               L3
2          100                               L1                L2
2          101                               L2                L2
2          102                               L1                L1
2          103                               L3                L4
3          100                               L2                L4
3          101                               L2                L5
3          102                               L1                L6
3          103                               L4                L7
[/code]
Thanks
-Ann

Answer 1

Hi,
Do you really need to store prev_status in test_detail?  You can always compute it on the fly, using the analytic LAG function, and you won't have to worry about re-computing it when test_detail is updated.
If test_detail will never be updated, and performance is important, then you may want to store prev_status.  Here's one way to do that.
When you're ready to archive the data from test_main, then run this INSERT statement:
INSERT INTO test_detail (trans_id, claim_id,  prev_status,      curr_status)
           SELECT        &2,     m.claim_id,  d.curr_status,    m.status
           FROM             test_main    m
           LEFT OUTER JOIN  test_detail  d  ON   d.claim_id  = m.claim_id
                                            AND  d.trans_id  = &1
Where &1 is the previous trans_id (the highest value already in test_detail), and &2 is the new trans_id (&1 + 1).
The first time you run this, when test_detail is empty, it doesn't matter what value you use for &1; you can use 0.
After you've confirmed that this worked, then you can start putting new data into test_main.
I assume that test_master and test_main are the same table.