you should re-desing your tables to able to store the two tables in one, if they're storing the same information. If you see that you need to duplicate rows to add new values into a record:
for example:
orders_table
email , itemname,quantity , orderdate
aaa@asd.com , plane , 4 , ____-__-__
aaa@asd.com , plane , 3 , ____-__-__
xcvxcv@asdélkasd.com , plane , ____-__-__
in this horrible table the emails and items are duplicated. You should store the items and emails in two separated table, meanwhile the orders table hold the quantities dates and the related information from the two tables.
email_table
e_id , email
1 , aaa@asd.com
2 , xcvxcv@asdélkasd.com
items_table
item_id , item_name
1 , plane
then the orders will be:
orders_table
order_id , email_id, item_id , orderdate
1 , 1 , 1 , ____-__-__
2 , 1 , 1 , ____-__-__
3 , 2 , 1 , ____-__-__