Passing resultser of one db adapter query to anoother db adapter query

Question

I would like achieve the following:
1) first query returns PO_Number, Batch_Number,..... etc. in the first query. But in this query the PO_NUMBER and batch number can come mutiple times because of other columns.
2) But I have to send a single notification for each Batch_Number/PO-number combination that comes from the above query.
to do that there can be a second db adapter with the query which will be like
select distinct PO_NUMBER, batch number from table1
where Batch_number and PO Number which are selected in the first query.
How to do that?
Is there any other way to fulfil the same requirement.

Answer 1

Hi there,
this is probably more one for the database SQL forums. It is a tricky one as you can't execute a select like:
select distinct PO_NUMBER, distinct BATCH_NUMBER, C3, C4, ....
Safest would be to do this query first:
select distinct PO_NUMBER, BATCH_NUMBER from tab
Then for each PO/BATCH read, execute the following select:
select * from tab where PO = ? and BATCH = ? and rownum <= 1;
However that will lead to a lot of queries to get the extra column info.
You can do it all in one query if you can find one other column in the table that is unique for a given PO/BATCH combination and sortable, i.e. assume it is named pk.
Then you can execute:
select * from TAB T0 where not exists (select * from TAB T1 where T0.PO = T1.PO and T0.BATCH = T1.BATCH and T1.pk< T0.pk)
It took a while but failing that you still can do it with one query. If a, b are the columns that need to be distinct (PO and BATCH), and c is say the other column, you could execute this:
with Q1 as (select distinct A, B, C, rownum as COUNTER from TAB) select T0.A, T0.B, T0.C from Q1 T0 where not exists(select * from Q1 T1 where T1.A= T0.A and T1.B = T0.B and T1.counter < T0.counter)
You can do all of this using the "execute pure SQL" option of the DbAdapter wizard. Just cut and paste in the SQL and it should generate the right XSD.
There is currently one issue with the pure SQL wizard, in that it doesn't recognize WITH. The query has to start with SELECT or it will think it is an update. So just wrap it with SELECT * FROM (...), i.e.
select * from (with Q1 as (select distinct A, B, C, rownum as COUNTER from TAB) select T0.A, T0.B, T0.C from Q1 T0 where not exists(select * from Q1 T1 where T1.A= T0.A and T1.B = T0.B and T1.counter < T0.counter))
That is if you want to do a one time select. If this is more for polling, I would look at the ExpertPolling sample on soasamples.samplecode.oracle.com for ideas. You can set the primary key to be PO/BATCH, and give custom poll and after read SQLs. The poll can be very similar to the one given here.
Thanks
Steve