Improving a SELECT query

Question

I have an interactive application that periodically feeds a legacy batch transaction application with data to keep it in sync with my app. For demonstrating my problem I am using a similar but much simpler example here, using two tables only: CUST and ORD. The CUST table contains customer specific data and the ORD table contains orders placed by each customer. The primary key of CUST table is the CU_CODE that is also a foreign key (OR_CU_CODE) in the ORD table. The PK of ORD table is the OR_CODE column. See their description below:
Table: CUST
Name               Null?     Type
CU_CODE          NOT NULL     VARCHAR2(6)
CU_TYPE          NOT NULL     VARCHAR2(2)
CU_NAME          NOT NULL     VARCHAR2(80)
CU_ADDR                    VARCHAR2(120)
Table: ORD
Name               Null?     Type
OR_CODE          NOT NULL     VARCHAR2(8)
OR_CU_CODE          NOT NULL     VARCHAR2(6)
OR_DATE          NOT NULL     DATE
OR_TERMS               VARCHAR2(40)
The legacy app needs to get both a customer and an order transaction for any order whose date is more recent than a given date. To create those transactions, I run a SELECT query like this:
SELECT 'UPD,CUST='||CU_CODE||',TYPE='||CU_TYPE||',NAME='||CU_NAME
||',ADDR='||CU_ADDR
FROM (SELECT DISTINCT CU_CODE, CU_TYPE, CU_NAME, CU_ADDR
FROM CUST, ORD WHERE OR_CU_CODE = CU_CODE
AND OR_DATE > SOME_DATE
ORDER BY 1)
UNION ALL
SELECT 'UPD,ORD='||OR_CODE||',CUST='||OR_CU_CODE||',DATE='
||TO_CHAR(OR_DATE, 'YYYYMMDD')||',TERMS='||OR_TERMS
FROM (SELECT OR_CODE, OR_CU_CODE, OR_DATE, OR_TERMS
FROM ORD WHERE OR_DATE > SOME_DATE
ORDER BY 2, 1);
This produces a batch update transaction file similar to the following:
UPD,CUST=CU1111,TYPE=COM,NAME=ACME,ADDR=ACME Address
UPD,CUST=CU2222,TYPE=RES,NAME=John Q,ADDR=John Q Address
UPD,CUST=CU3333,TYPE=GOV,NAME=IRS,ADDR=IRS Address
UPD,ORD=OR001234,CUST=CU1111,DATE=20061204,TERMS=Term1
UPD,ORD=OR001235,CUST=CU1111,DATE=20061206,TERMS=Term1
UPD,ORD=OR001236,CUST=CU1111,DATE=20061207,TERMS=Term1
UPD,ORD=OR002234,CUST=CU2222,DATE=20061205,TERMS=Term2
UPD,ORD=OR002235,CUST=CU2222,DATE=20061207,TERMS=Term2
UPD,ORD=OR003237,CUST=CU3333,DATE=20070102,TERMS=Term3
Both transaction types are sorted by the customer code first but customer update transactions also need a DISTINCT clause because we only want to send one custumer update per customer even if there were more orders placed by that customer.
This thing has been working fine in most cases except when a large transaction file is generated because the legacy app can only handle input files of only certain max. size. In such cases the operators need to manually split up the file into several smaller ones but still making sure that each file segment has customer and order transactions belonging to the same customers only. This can be really tedious with hundreads of customers and their orders. The file splitting would be much easier if I could rewrite the original SELECT statement to produce the transaction data in the following order:
UPD,CUST=CU1111,TYPE=COM,NAME=ACME,ADDR=ACME Address
UPD,ORD=OR001234,CUST=CU1111,DATE=20061204,TERMS=Term1
UPD,ORD=OR001235,CUST=CU1111,DATE=20061206,TERMS=Term1
UPD,ORD=OR001236,CUST=CU1111,DATE=20061207,TERMS=Term1
UPD,CUST=CU2222,TYPE=RES,NAME=John Q,ADDR=John Q Address
UPD,ORD=OR002234,CUST=CU2222,DATE=20061205,TERMS=Term2
UPD,ORD=OR002235,CUST=CU2222,DATE=20061207,TERMS=Term2
UPD,CUST=CU3333,TYPE=GOV,NAME=IRS,ADDR=IRS Address
UPD,ORD=OR003237,CUST=CU3333,DATE=20070102,TERMS=Term3
Here a given customer update transaction would be followed by all orders for that customer and so on.
I want the new query also in pure SQL, not in PL SQL. As dealing with DB and Oracle is only a small part of my job, I just can't figure out a solution to this problem. I suspect many of the regulars here can help me.
Thanks,
Joe
PS: Sorry, the table descriptions looked much better in the edit screen but I hope you can still figure it out from the display window.

Answer 1

Try something like the following (not tested)
SELECT transaction FROM (
SELECT CU_CODE,1,'UPD,CUST='||CU_CODE||',TYPE='||CU_TYPE||',NAME='||CU_NAME
||',ADDR='||CU_ADDR transaction
FROM (SELECT DISTINCT CU_CODE, CU_TYPE, CU_NAME, CU_ADDR
FROM CUST, ORD WHERE OR_CU_CODE = CU_CODE
AND OR_DATE > SOME_DATE)
UNION ALL
SELECT OR_CU_CODE,2,'UPD,ORD='||OR_CODE||',CUST='||OR_CU_CODE||',DATE='
||TO_CHAR(OR_DATE, 'YYYYMMDD')||',TERMS='||OR_TERMS transaction
FROM (SELECT OR_CODE, OR_CU_CODE, OR_DATE, OR_TERMS
FROM ORD WHERE OR_DATE > SOME_DATE)
ORDER BY 1,2;Basically, I added some columns to your query for sorting purposes then used that query as an inline view to only get the data you are interested in. Hope it runs. If not, let me know and I'll create the table and actually test it.