Copy and Cascade insert using PL/SQL - sql

Question

Given data structure:
I have the following table My_List, where Sup_ID is Primary Key
My_List
+--------+----------+-----------+
| Sup_ID | Sup_Name | Sup_Code |
+--------+----------+-----------+
| 1 | AA | 23 |
| 2 | BB | 87 |
| 3 | CC | 90 |
+--------+----------+-----------+
And the following table _MyList_details, where Buy_ID is Primary Key and Sup_ID is Foreign Key points at My_List.Sup_ID
My_List_details
+--------+--------+------------+------------+------------+
| Buy_ID | Sup_ID | Sup_Detail | Max_Amount | Min_Amount |
+--------+--------+------------+------------+------------+
| 23 | 1 | AAA | 1 | 10 |
| 33 | 2 | BBB | 11 | 20 |
| 43 | 3 | CCC | 21 | 30 |
+--------+--------+------------+------------+------------+
Finally, I have the table My_Sequence as follow:
My_Sequence
+-----+------+
| Seq | Name |
+-----+------+
| 4 | x |
| 5 | y |
| 6 | z |
+-----+------+
---------------------------------------------------
Objectives
Write PL/SQL script to:
Using a cursor, I need to copy My_List records and re-insert it with the new Sup_ID copied from My_Sequence.Seq.
I need to copy My_List_details records and re-insert them with the new Sup_ID foreign key.
------------------------------------------------------------------------------
Expected Outcome
My_List
+--------+----------+----------+
| Sup_ID | Sub_Name | Sub_Code |
+--------+----------+----------+
| 1 | AA | 23 |
| 2 | BB | 87 |
| 3 | CC | 90 |
| 4 | AA | 23 |
| 5 | BB | 87 |
| 6 | CC | 90 |
+--------+----------+----------+
My_List_details
+--------+--------+------------+------------+------------+
| Buy_ID | Sup_ID | Sub_Detail | Max_Amount | Min_Amount |
+--------+--------+------------+------------+------------+
| 23 | 1 | AAA | 1 | 10 |
| 33 | 2 | BBB | 11 | 20 |
| 43 | 3 | CCC | 21 | 30 |
| 53 | 4 | AAA | 1 | 10 |
| 63 | 5 | BBB | 11 | 20 |
| 73 | 6 | CCC | 21 | 30 |
+--------+--------+------------+------------+------------+
What I have started with is the following:
DECLARE
NEW_Sup_ID Sup_ID%type := Seq;
c_Sup_Name Sup_Name%type;
c_Sup_Code Sup_Code%type;
c_Buy_ID Buy_ID%type;
c_Sup_Detail Sup_Detail%type;
c_Max_Amount Max_Amount%type
c_My_Min_Amount Min_Amount%type
CURSOR c_My_List
IS
SELECT * FROM My_List;
CURSOR c_My_List_details
IS
SELECT * FROM My_List_details
BEGIN
FETCH c_My_List INTO NEW_Sup_ID, c_Sup_Name, c_Sup_Code;
INSERT INTO My_List;
FETCH c_My_List_details INTO c_Buy_ID, NEW_Sup_ID, c_Sup_Detail, c_Max_Amount, c_Min_Amount
INSERT INTO My_List_details
END;
/
Aside from the syntax errors, I do not see my script copy row by row and insert them to both tables accordingly. Further, the number of My_Sequence records is bigger than the number of My_List records. So what I need is, if My_List records are 50, I need the script to copy the first 50 Seq from My_Sequence.
---------------------------------------------------------------------------------
Question
How to achieve this result? I have searched and found Tom Kyte for cascade update but I am not sure if I do need to use this package, I am a bit beginner in PL/SQL and it is a bit complicated for me to utilize such a comprehensive package. Further, it's for cascade update and my case is about re-insert. I'd appreciate any help

Answer 1

The following Sql Statements will perform the task on the schema defined at this SqlFiddle. Note that I have changed a couple of field and table names - because they clash with Oracle terms. SqlFiddle seems to have some problems with my code, but it has been tested on another (amphibious) client which shall remain nameless.
The crucial point (As I said in my comments) is deriving a rule to map old sequence number to new. The view SEQUENCE_MAP performs this task in the queries below.
You may be disappointed by my reply because it depends upon there being the exact same number of sequence records as LIST/LIST_DETAILS, and hence it can only be run once. Your final PL/SQL can perform the necessary checks, I hope.
Hopefully it is a matter of refining the sequence_map logic to get you where you want to be.
Avoid using cursors; ideally when manipulating relational data you need to think in terms of sets of data rather than rows. This is because if you use set-thinking Oracle can do its magic in optimising, parallelising and so-on. Oracle is brilliant at scaling up - If a table is split over multiple disks, for example, it may process your request with data from the multiple disks simultaneously. If you force it into a row-by-row, procedural logic you may find that the applications you write do not scale up well.
CREATE OR REPLACE VIEW SEQUENCE_MAP AS (
SELECT OLD_SEQ, NEW_SEQ FROM
(
( SELECT ROWNUM AS RN, SUP_ID AS OLD_SEQ FROM
(SELECT SUP_ID FROM LIST ORDER BY SUP_ID) ) O
JOIN
( SELECT ROWNUM AS RN, SUP_ID AS NEW_SEQ FROM
(SELECT SEQ AS SUP_ID FROM SEQUENCE_TABLE ORDER BY SEQ) ) N
ON N.RN = O.RN
)
);
INSERT INTO LIST
(
SELECT
NEW_SEQ, SUB_NAME, SUB_CODE
FROM
SEQUENCE_MAP
JOIN LIST L ON
L.SUP_ID = SEQUENCE_MAP.OLD_SEQ
);
INSERT INTO LIST_DETAILS
(
SELECT
BUY_ID, NEW_SEQ, SUB_DETAIL, MAX_FIELD, MIN_FIELD
FROM
SEQUENCE_MAP
JOIN LIST_DETAILS L ON
L.SUP_ID = SEQUENCE_MAP.OLD_SEQ
);

Answer 2

I would do 2 inner loops, and search the next sequence to use.
I imagine the new buy_id is assigned via trigger using a sequence, or something equivalent, else you'll have to generate it in your code.
I have no Oracle database available to test it, so don't pay attention to syntax.
DECLARE
NEW_Sup_ID Sup_ID%type := Seq;
c_Sup_ID Sup_ID%type := Seq;
c_Sup_Name Sup_Name%type;
c_Sup_Code Sup_Code%type;
c_Buy_ID Buy_ID%type;
c_Sup_Detail Sup_Detail%type;
c_Max_Amount Max_Amount%type;
c_My_Min_Amount Min_Amount%type;
CURSOR c_My_List
IS
SELECT * FROM My_List;
CURSOR c_My_List_details
IS
SELECT * FROM My_List_details where sup_id=c_Sup_ID;
BEGIN
for c_My_List IN c_Sup_ID, c_Sup_Name, c_Sup_Code loop
select min(seq) from My_sequence into NEW_Sup_ID;
INSERT INTO My_List (sup_id,...) values (NEW_Sup_ID,...);
for c_My_List_details IN c_Buy_ID, NEW_Sup_ID, c_Sup_Detail, c_Max_Amount, c_Min_Amount loop
INSERT INTO My_List_details (sup_id, ...) values (NEW_Sup_ID,...);
end loop;
deelte from from My_sequence where seq= NEW_Sup_ID;
end loop;
commit;
END;
/