MySQL COUNT query with or without HAVING clause giving same results - mysql

Question

I am having issues with an SQL query which involves a COUNT and a HAVING clause.
The objective is to get the count of all products that have stock and are also not being 'picked' for another customer hence the HAVING clause.
However, when the query is run both with and without the HAVING clause at the end of the query below I get the same COUNT as the result.
To ensure that the COUNT results should not be the same I tried running queries to check if there were products that were out of stock since all products will need to be in stock for the results to match up and confirmed that there were definitely products out of stock.
SELECT
COUNT(DISTINCT p.product_id)
FROM product p
LEFT JOIN product_variant pv
ON pv.product_variant_id = p.product_id
LEFT JOIN depot_product_stock dps
ON dps.product_variant_id = pv.product_variant_id
LEFT JOIN (
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
WHERE pii.STATUS IN ('not picked')
) AS pickListNotPicked
ON pickListNotPicked.product_variant_id = pv.product_variant_id
LEFT JOIN (
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
WHERE pii.STATUS IN ('picked')
AND pii.date_picked > NOW() - INTERVAL 2 WEEK
AND packi.picklist_id IS NULL
) AS pickListPicked
ON pickListPicked.product_variant_id = pv.product_variant_id
LEFT JOIN (
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
WHERE packi.`status` IN ('new', 'in progress')
) AS pickListInProgress
ON pickListInProgress.product_variant_id = pv.product_variant_id
WHERE p.deleted = 0
HAVING SUM(dps.physical_stock)
- ifnull(SUM(pickListNotPicked.quantity),0)
- ifnull(SUM(pickListPicked.quantity) ,0)
- ifnull(SUM(pickListInProgress.quantity) ,0)
> 0
I don't know where I'm going wrong with the query. Kindly help. Thanks.

Answer 1

I don't think you want a having clause. Your query is just returning one row. That having clause might have it return zero rows instead of 1 row. And, the having clause is looking over all the products.
Perhaps you want a where clause instead:
WHERE p.deleted = 0 AND
(dps.physical_stock - ifnull(pickListNotPicked.quantity, 0) -
ifnull(pickListPicked.quantity, 0)
ifnull(pickListInProgress.quantity, 0)
) > 0
Note that I prefer replacing ifnull() with coalesce(). (When given the option, I generally prefer the ANSI standard functions.)

Answer 2

I think the issue is that you are mixing up all the quantities to check.
Your query appears to be trying to find a count of products where the physical stock quantity is not equal the the sum of the quantities in various status'.
The trouble is that you are SUMing up all the stock quanties and pick quantities for ALL products. Thus if any single product has a mismatch it will be reflected in the check in the HAVING clause.
I think you need one large sub query to get all the product ids where the quantities do not match, and then do a count based on that.
Something like this (untested).
SELECT COUNT(product_id)
FROM
(
SELECT p.product_id
FROM product p
LEFT JOIN product_variant pv
ON pv.product_variant_id = p.product_id
LEFT JOIN depot_product_stock dps
ON dps.product_variant_id = pv.product_variant_id
LEFT JOIN
(
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
WHERE pii.STATUS IN ('not picked')
) AS pickListNotPicked
ON pickListNotPicked.product_variant_id = pv.product_variant_id
LEFT JOIN
(
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
WHERE pii.STATUS IN ('picked')
AND pii.date_picked > NOW() - INTERVAL 2 WEEK
AND packi.picklist_id IS NULL
) AS pickListPicked
ON pickListPicked.product_variant_id = pv.product_variant_id
LEFT JOIN
(
SELECT pii.quantity, pii.product_variant_id
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
WHERE packi.`status` IN ('new', 'in progress')
) AS pickListInProgress
ON pickListInProgress.product_variant_id = pv.product_variant_id
WHERE p.deleted = 0
GROUP BY p.product_id
HAVING SUM(dps.physical_stock)
- IFNULL(SUM(pickListNotPicked.quantity),0)
- IFNULL(SUM(pickListPicked.quantity) ,0)
- IFNULL(SUM(pickListInProgress.quantity) ,0)
> 0
) sub0
You might be able to remove some of the sub queries you already have like this:-
SELECT COUNT(DISTINCT p.product_id)
FROM
(
SELECT p.product_id
FROM product p
LEFT JOIN product_variant pv
ON pv.product_variant_id = p.product_id
LEFT JOIN depot_product_stock dps
ON dps.product_variant_id = pv.product_variant_id
LEFT JOIN
(
SELECT pii.product_variant_id,
SUM(IF(pii.STATUS IN ('not picked')), quantity, 0) AS pickListNotPicked_qty,
SUM(IF(pii.STATUS IN ('picked') AND pii.date_picked > NOW() - INTERVAL 2 WEEK AND packi.picklist_id IS NULL), quantity, 0) AS pickListPicked_qty,
SUM(IF(packi.`status` IN ('new', 'in progress')), quantity, 0) AS pickListInProgress_qty
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
GROUP BY pii.product_variant_id
) AS quantities
ON quantities.product_variant_id = pv.product_variant_id
WHERE p.deleted = 0
GROUP BY p.product_id
HAVING SUM(dps.physical_stock)
- IFNULL(SUM(pickListNotPicked_qty),0)
- IFNULL(SUM(pickListPicked_qty) ,0)
- IFNULL(SUM(pickListInProgress_qty) ,0)
) sub0
This might be further cleaned down to :-
SELECT COUNT(DISTINCT p.product_id)
FROM
(
SELECT p.product_id
FROM product p
LEFT JOIN product_variant pv
ON pv.product_variant_id = p.product_id
LEFT JOIN depot_product_stock dps
ON dps.product_variant_id = pv.product_variant_id
LEFT JOIN
(
SELECT pii.product_variant_id,
SUM(quantities) AS relevant_qty
FROM `picklist_item` pii
LEFT JOIN `packing` packi ON packi.picklist_id = pii.picklist_id
WHERE pii.STATUS = 'not picked'
OR (pii.STATUS = 'picked' AND pii.date_picked > NOW() - INTERVAL 2 WEEK AND packi.picklist_id IS NULL)
OR packi.`status` IN ('new', 'in progress')
GROUP BY pii.product_variant_id
) AS quantities
ON quantities.product_variant_id = pv.product_variant_id
WHERE p.deleted = 0
GROUP BY p.product_id
HAVING SUM(dps.physical_stock)
- IFNULL(SUM(relevant_qty) ,0)
) sub0
Note that I am slightly unsure of your sum logic if I understand your requirement correctly. You could items that are not picked and items picked in the last week. You also count items that have a status of new or in progress, yet it would seem these items could already have been counted as picked / not picked, hence double counted for the sums and ensuring that the final sums did not match and the items were used for the count of product ids.