sku is not correct concept

[nasservb]

sku is specific identifier for each instance of each product .
in your system sku is like product-serial (one for all instance of product that have same type) .
you need to create separate table like product_sku to store all unique sku for each instance of each product.
product_sku structure :
sku--------------#pk
product_id-------#fk to product
created_at--------timestamp
is_generated_qr_code------boolean

for product with 54 quantity we need to insert 54 record to product_sku table .

when we create order we can create new table like
order_item_sku with this structure:
id-------#pk
order_item_id-----#fk to order item
sky------------------#fk to product_sku

by adding this tables we can track any product instance status.