How to duplicate data from application level? Not database level - mysql

Question

I am stuck for duplicate data from my application.
Let's say I have:
PetBooks Table:
id
book_name
Pet:
id
book_id
code
name
type
Petbooks
1 MyPet
Pet:
1 1 CAT1 Josh Cat
2 1 CAT2 Ron Cat
3 1 DOG1 Max Dog
Question 1:
How can I duplicate Petbook and all its pets?
So After I duplicate the petbook, it should look like
Petbooks
1 MyPet
2 MyPet(Copy)
Pet:
1 1 CAT1 Josh Cat
2 1 CAT2 Ron Cat
3 1 DOG1 Max Dog
4 2 CAT1 Josh Cat
5 2 CAT2 Ron Cat
6 2 DOG1 Max Dog
The solution I think is, to get all of the pet where book_id = 1, then looping and insert one by one, but it's so slow especially when there are a lot of data.

Answer 1

Well, you can do this somewhat painfully -- assuming that ids are assigned automatically and some column other than id is unique in the original data. Let me call that column name.
Then:
insert into petbooks (book_name)
select concat('Copy of ', book_name)
from petbooks;
Then for pets, we have to look up the new id. We can create a look-up table on the fly using aggregation:
insert into pets (book_id, code, name, type)
select pb.max_id, code, name, type)
from pets p join
(select name, min(id) as min_id, max(id) as max_id
from petbooks
group by name
) pb
on pb.min_id = p.book_id

Answer 2

You may handle the relationship manually one by one, and combine them to a procedure. You may use the LAST_INSERT_ID() function to get the latest id. For example:
CREATE PROCEDURE copy_petbook(petbook_id INT)
BEGIN
INSERT INTO PetBooks (book_name)
SELECT CONCAT(book_name, '(Copy)')
FROM Petbooks
WHERE id = petbook_id;
DECLARE last_insert_id BIGINT;
SET last_insert_id = LAST_INSERT_ID();
INSERT INTO Pet (book_id, code, name, type)
SELECT lid.last_insert_id , code, name, type
FROM Pet JOIN (SELECT last_insert_id) as lid
WHERE book_id = petbook_id;
END
If you want to use UUIDs for the id column, you may change the signature to CHAR(36) and then use the UUID() function:
CREATE PROCEDURE copy_petbook(petbook_id CHAR(36))
BEGIN
DECLARE uuid CHAR(36);
-- Generate an UUID which has not been used.
REPEAT
SET uuid = UUID();
UNTIL (SELECT COUNT(*) FROM PetBooks WHERE id = uuid) = 0 END REPEAT;
-- Insert rows with the UUID
INSERT INTO PetBooks (id, book_name)
SELECT u.uuid, CONCAT(book_name, '(Copy)')
FROM Petbooks JOIN (SELECT uuid) as u
WHERE id = petbook_id;
INSERT INTO Pet (book_id, code, name, type)
SELECT u.uuid, code, name, type
FROM Pet JOIN (SELECT uuid) as u
WHERE book_id = petbook_id;
END
You may generate more UUIDs in the same way if you are also using an UUID for the id column in other tables.
Finally, just call the procedure:
CALL copy_petbook(/* Put the id here. */);