using joins together with aggregates, and retrieving rows when no aggregate exists - mysql

Question

The following query on my MySQL tables returns rows from the purchaseorder table that have corresponding entries in the deliveryorder table. How do I construct this query so that I get rows from the purchaseorder table even if no corresponding rows exist in the deliveryorder table? If the users want to see sql table CREATE statements, I can post those, but I'm not posting now as it really makes the question too big.
SELECT
`purchaseorder`.`id` AS `po_id`,
`purchaseorder`.`order_quantity` AS `po_order_quantity`,
`purchaseorder`.`applicable_approved_unit_rate` AS `po_unit_rate`,
`purchaseorder`.`applicable_sales_tax_rate` AS `po_tax_rate`,
`purchaseorder`.`order_date` AS `po_order_date`,
`purchaseorder`.`remarks` AS `po_remarks`,
`purchaseorder`.`is_open` AS `po_is_open`,
`purchaseorder`.`is_active` AS `po_is_active`,
`purchaseorder`.`approved_rate_id` AS `po_app_rate_id`,
`supplier`.`name` AS `sup_name`,
SUM(`deliveryorder`.`quantity`) AS `total_ordered`
FROM `purchaseorder`
LEFT JOIN `deliveryorder` ON (`deliveryorder`.`purchase_order_id` = `purchaseorder`.`id`)
INNER JOIN `approvedrate` ON (`purchaseorder`.`approved_rate_id` = `approvedrate`.`id`)
INNER JOIN `supplier` ON (`approvedrate`.`supplier_id` = `supplier`.`id`)
WHERE (
`purchaseorder`.`is_active` = 1
AND `purchaseorder`.`is_open` = 1
AND `deliveryorder`.`is_active` = 1
AND `approvedrate`.`material_id` = 2
)
HAVING `purchaseorder`.`order_quantity` >= `total_ordered` + 1

Answer 1

You have an aggregating function but no GROUP BY clause, which is wierd, but anyway - something like this? Oops - edited...
SELECT po.id po_id
, po.order_quantity po_order_quantity
, po.applicable_approved_unit_rate po_unit_rate
, po.applicable_sales_tax_rate po_tax_rate
, po.order_date po_order_date
, po.remarks po_remarks
, po.is_open po_is_open
, po.is_active po_is_active
, po.approved_rate_id po_app_rate_id
, s.name sup_name
, SUM(do.quantity) total_ordered
FROM purchaseorder po
LEFT
JOIN deliveryorder do
ON do.purchase_order_id = po.
AND do.is_active = 1
LEFT
JOIN approvedrate ar
ON ar.id = po.approved_rate_id
AND ar.material_id = 2
LEFT
JOIN supplier s
ON s.id = ar.supplier_id
WHERE po.is_active = 1
AND po.is_open = 1
HAVING po.order_quantity >= total_ordered + 1

Answer 2

I couldn't work out how to get the desired results all in one query, but ended up using the following two queries to fulfill my requirements: -
1st query
SELECT
pot.`id` AS `po_id`,
pot.`order_quantity` AS `po_order_quantity`,
pot.`applicable_approved_unit_rate` AS `po_unit_rate`,
pot.`applicable_sales_tax_rate` AS `po_tax_rate`,
pot.`is_open` AS `po_is_open`,
pot.`is_active` AS `po_is_active`,
st.`id` AS `sup_id`,
st.`name` AS `sup_name`,
SUM(dot.`quantity`) AS `total_ordered`
FROM `purchaseorder` pot
INNER JOIN `deliveryorder` dot ON (dot.`purchase_order_id` = pot.`id`)
INNER JOIN `approvedrate` art ON (pot.`approved_rate_id` = art.`id`)
INNER JOIN `supplier` st ON (art.`supplier_id` = st.`id`)
WHERE (
pot.`is_active` = 1
AND pot.`is_open` = 1
AND art.`material_id` = #materialid
AND art.`in_effect` = 1
AND art.`is_active` = 1
AND dot.`is_active` = 1
AND st.`is_active` = 1
)
HAVING pot.`order_quantity` >= `total_ordered` + #materialquantity
2nd query
SELECT
pot.`id` AS `po_id`,
pot.`order_quantity` AS `po_order_quantity`,
pot.`applicable_approved_unit_rate` AS `po_unit_rate`,
pot.`applicable_sales_tax_rate` AS `po_tax_rate`,
pot.`is_open` AS `po_is_open`,
pot.`is_active` AS `po_is_active`,
st.`id` AS `sup_id`,
st.`name` AS `sup_name`,
0 AS `total_ordered`
FROM `purchaseorder` pot
INNER JOIN `approvedrate` art ON (pot.`approved_rate_id` = art.`id`)
INNER JOIN `supplier` st ON (art.`supplier_id` = st.`id`)
WHERE (
pot.`is_active` = 1
AND pot.`is_open` = 1
AND art.`material_id` = #materialid
AND art.`in_effect` = 1
AND art.`is_active` = 1
AND st.`is_active` = 1
AND pot.`order_quantity` >= #materialquantity
AND pot.`id` NOT IN
(
SELECT dot.`purchase_order_id`
FROM `deliveryorder` dot
WHERE dot.is_active = 1
)
)