Sum Qtys from 3 tables - mysql

Question

The view below does not return correct results. I am trying to get the sum of Picked, Printed & Scanned grouped by Plan_Id & PartNum. I need to return the correct totals regardless if there are corresponding records in the child tables. I know how to do it if I use three different views and join them, but how do i do it all in a single view? Any help appreciated.
SELECT
`prod_plan`.`Prp_ProdPlanId` AS `PlanId`,
`prod_plan`.`Prp_PartNum` AS `PartNum`,
sum(`prod_plan`.`Prp_Picked`) AS `Picked`,
sum(`printed`.`PtQty`) AS `Printed`,
sum(`scanned`.`PtQty`) AS `Scanned`
FROM
(
(
`prod_plan`
LEFT JOIN `product_trans` `printed` ON (
(
(
`printed`.`PtPlanId` = `prod_plan`.`Prp_ProdPlanId`
)
AND (
`printed`.`PtPartNum` = `prod_plan`.`Prp_PartNum`
)
)
)
)
LEFT JOIN `product_trans` `scanned` ON (
(
(
`scanned`.`PtPlanId` = `prod_plan`.`Prp_ProdPlanId`
)
AND (
`scanned`.`PtPartNum` = `prod_plan`.`Prp_PartNum`
)
)
)
)
WHERE
(
(
`printed`.`PtPart` = 'Barcode Print'
)
AND (
`scanned`.`PtPart` = 'Barcode Scan'
)
)
GROUP BY
`prod_plan`.`Prp_ProdPlanId`,
`prod_plan`.`Prp_PartNum`

Answer 1

You need to check PtPart in the ON clauses. Otherwise, you won't get the rows with no matches in the child tables, because those columns will be NULL.
SELECT
`prod_plan`.`Prp_ProdPlanId` AS `PlanId`,
`prod_plan`.`Prp_PartNum` AS `PartNum`,
sum(`prod_plan`.`Prp_Picked`) AS `Picked`,
sum(`printed`.`PtQty`) AS `Printed`,
sum(`scanned`.`PtQty`) AS `Scanned`
FROM `prod_plan`
LEFT JOIN `product_trans` `printed`
ON `printed`.`PtPlanId` = `prod_plan`.`Prp_ProdPlanId`
AND `printed`.`PtPartNum` = `prod_plan`.`Prp_PartNum`
AND `printed`.`PtPart` = 'Barcode Print'
LEFT JOIN `product_trans` `scanned`
ON `scanned`.`PtPlanId` = `prod_plan`.`Prp_ProdPlanId`
AND `scanned`.`PtPartNum` = `prod_plan`.`Prp_PartNum`
AND `scanned`.`PtPart` = 'Barcode Scan'
GROUP BY
`prod_plan`.`Prp_ProdPlanId`,
`prod_plan`.`Prp_PartNum`

Answer 2

Here is what I have done. Below are 3 views that work correctly.
v_trans_printed:
SELECT
product_trans.PtPlanId AS PlanId,
product_trans.PtLot AS Lot,
product_trans.PtPartNum AS PartNum,
Sum(product_trans.PtQty) AS Printed
FROM
product_trans
WHERE
product_trans.PtPart = 'Barcode Print'
GROUP BY
product_trans.PtPlanId,
product_trans.PtLot,
product_trans.PtPartNum
v_trans_scanned:
SELECT
product_trans.PtPlanId AS PlanId,
product_trans.PtLot AS Lot,
product_trans.PtPartNum AS PartNum,
Sum(product_trans.PtQty) AS Scanned
FROM
product_trans
WHERE
product_trans.PtPart = 'Barcode Scan'
GROUP BY
product_trans.PtPlanId,
product_trans.PtLot,
product_trans.PtPartNum
And here I put them all together. This returns the correct results:
vSELECT
prod_plan.Prp_ProdPlanId AS PlanId,
prod_plan.Prp_Lot AS Lot,
prod_plan.Prp_PartNum AS PartNum,
Sum(prod_plan.Prp_Picked) AS Picked,
Printed.Printed AS Printed,
Scanned.Scanned AS Scanned
FROM
prod_plan
LEFT JOIN v_trans_printed AS Printed ON Printed.PlanId = prod_plan.Prp_ProdPlanId AND Printed.Lot = prod_plan.Prp_Lot AND Printed.PartNum = prod_plan.Prp_PartNum
LEFT JOIN v_trans_scanned AS Scanned ON Scanned.PlanId = prod_plan.Prp_ProdPlanId AND Scanned.Lot = prod_plan.Prp_Lot AND Scanned.PartNum = prod_plan.Prp_PartNum
GROUP BY
prod_plan.Prp_ProdPlanId,
prod_plan.Prp_Lot,
prod_plan.Prp_PartNum
But it would be better if I could use one view.
Note: I left out Lot originally by accident. But it didn't affect the results w. the sample data set.