How can I fix my table to make a expiration of medicine? - mysql

Question

I'm doing an inventory system of drug store. And now I'm trying to do the expiration of medicine. I want to show you my table. Maybe you have an idea of how to fix my tables. I put the expiration date in tbl_received_order. When I received a medicine it will insert into tbl_medicine. What if the customer bought 50 pieces of paracetamol or supplier_med_id is equal to 3. And after two months the medicine received will be expired. I use DATE(NOW()) > tbl_received_order.expiration_date to get all the expired medicine.
My problem is that the qty is not tally to rec_qty when the medicine expired. Just for below example, I have 100 pcs. on my initial inventory. But later on, 50 pcs. was sold. Why is it 100 pcs.is still reflecting on my inventory of medicines for expiration, instead of 50pcs. How can I fix my table? Can somebody help me with my problem?
The is my table
tbl_medicine
med_id supplier_med_id qty status branch_id
1 3 50 Active 1
2 7 100 Active 1
3 9 100 Active 1
tbl_received_order
received_id user_id purchase_order_id date_received
RO20190001 1 PO20190001 2019-05-04
tbl_received_order_details
id received_id supplier_med_id rec_qty expiration_date
1 RO20190001 3 100 2019-11-04
2 RO20190001 7 100 2019-11-04
3 RO20190001 9 100 2019-11-04
1 RO20190002 3 50 2019-11-04
2 RO20190002 7 50 2019-11-04
3 RO20190002 9 50 2019-11-04
tbl_transaction
transaction_id customer_id user_id transaction_date branch_id
0001 CU2018001 1 2019-09-04 1
0002 CU2018001 1 2019-09-04 1
0003 CU2018001 1 2019-09-04 1
tbl_transaction_details
details_id transaction_id supplier_med_id qty price total_price
1 0001 3 50 10.00 500
2 0002 3 10 10.00 100
3 0003 3 10 10.00 100

Answer 1

You can get the accurate quantity by using a JOIN.
SELECT orderd.expiration_date, orderd.rec_qty - SUM(trans.qty) AS inventory_left
FROM tbl_received_order_details AS orderd
JOIN tbl_transaction_details AS trans
ON orderd.supplier_med_id = trans.supplier_med_id
WHERE orderd.supplier_med_id = 3
AND orderd.expiration_date < '2019-11-05'
Join tbl_received_order_details and tbl_transaction_details using supplier_med_id.
Filter the records with medicine id '3' and an expiration date.
Since there can be more than 1 transaction for a particular medicine, we need to SUM the quantity sold and subtract it from total quantity to get what's left.
Update 1
Above query will get expired medicines for the ones sold. To get quantity left for all inventories sold, use GROUP BY.
SELECT orderd.expiration_date, orderd.rec_qty - SUM(trans.qty) AS inventory_left
FROM tbl_received_order_details AS orderd
JOIN tbl_transaction_details AS trans
ON orderd.supplier_med_id = trans.supplier_med_id
WHERE orderd.expiration_date < '2019-11-05'
GROUP BY orderd.supplier_med_id
UPDATE 2
To get all left inventories that are expired whether they are sold or not, use LEFT JOIN. COALESCE(trans.qty, 0) will return first NOT NULL value. So if a medicine is never sold, it will not have any entry in transaction table which will return qty as NULL. In such cases, we will subtract zero from rec_qty which in turn will get complete rec_qty as left overs.
SELECT orderd.expiration_date, orderd.rec_qty - SUM(COALESCE(trans.qty, 0)) AS inventory_left
FROM tbl_received_order_details AS orderd
LEFT JOIN tbl_transaction_details AS trans
ON orderd.supplier_med_id = trans.supplier_med_id
WHERE orderd.expiration_date < '2019-11-05'
GROUP BY orderd.supplier_med_id