🚀 go-pugleaf

Hello,
I am looking for a logical and fast way to make the following

I have 5 tables:
1- inventory items (item code, name, etc...)

2- purchased invoices (date, invoice no, etc...)
3- detail table for table purchased invoices to store invoices items 
(item code, quantity, price, etc...)

4- sold invoices (date, invoice no, etc...)
5- detail table for table sold invoices to store invoices items (item 
code, quantity, price, etc...)

now I need to store all the items from table 1 into the following table 
ordered by date so I can calculate average cost

6- table average cost:

Date        purchased qty           cost price            sold qty
-----       --------------            ----------            ---------
5/6          50                             40.5                    0
7/6            40                           42                       
23      and so on

I am thinking to for using insert into with select expression for table 
2 and 3 but I need to also insert quantity sold for the same date how I 
can do that ?, again speed is critical

Thanks