Complex Full Outer Join - sql

Question

Sigh ... can anyone help? In the SQL query below, the results I get are incorrect. There are three (3) labor records in [LaborDetail]
Hours / Cost
2.75 / 50.88
2.00 / 74.00
1.25 / 34.69
There are two (2) material records in [WorkOrderInventory]
Material Cost
42.75
35.94
The issue is that the query incorrectly returns the following:
sFunction cntWO sumLaborHours sumLaborCost sumMaterialCost
ROBOT HARNESS 1 12 319.14 236.07
What am I doing wrong in the query that is causing the sums to be multiplied? The correct values are sumLaborHours = 6, sumLaborCost = 159.57, and sumMaterialCost = 78.69. Thank you for your help.
SELECT CASE WHEN COALESCE(work_orders.location, Work_Orders_Archived.location) IS NULL
THEN '' ELSE COALESCE(work_orders.location, Work_Orders_Archived.location) END AS sFunction,
(SELECT COUNT(*)
FROM work_orders
FULL OUTER JOIN Work_Orders_Archived
ON work_orders.order_number = Work_Orders_Archived.order_number
WHERE COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = '919630') AS cntWO,
SUM(Laborhours) AS sumLaborHours,
SUM(LaborCost) AS sumLaborCost,
SUM(MaterialCost*MaterialQuanity) AS sumMaterialCost
FROM work_orders
FULL OUTER JOIN Work_Orders_Archived
ON work_orders.order_number = Work_Orders_Archived.order_number
LEFT OUTER JOIN
(SELECT HoursWorked AS Laborhours, TotalDollars AS LaborCost, WorkOrderNo
FROM LaborDetail) AS LD
ON COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = LD.WorkOrderNo
LEFT OUTER JOIN
(SELECT UnitCost AS MaterialCost, Qty AS MaterialQuanity, OrderNumber
FROM WorkOrderInventory) AS WOI
ON COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = WOI.OrderNumber
WHERE COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = '919630'
GROUP BY CASE WHEN COALESCE(work_orders.location, Work_Orders_Archived.location) IS NULL
THEN '' ELSE COALESCE(work_orders.location, Work_Orders_Archived.location) END
ORDER BY sFunction

Answer 1

Try using the SUM function inside a derived table subquery when doing the full join to "WorkOrderInventory" like so...
select
...
sum(hrs) as sumlaborhrs,
sum(cost) as sumlaborcost,
-- calculate material cost in subquery
summaterialcost
from labordetail a
full outer join
(select ordernumber, sum(materialcost) as summaterialcost
from WorkOrderInventory
group by ordernumber
) b on a.workorderno = b.ordernumber
i created a simple sql fiddle to demonstrate this (i simplified your query for examples sake)

Answer 2

Looks to me that work_orders and work_orders_archived contains the same thing and you need both tables as if they were one table. So you could instead of joining create a UNION and use it as if it was one table:
select location as sfunction
from
(select location
from work_orders
union location
from work_orders_archived)
Then you use it to join the rest. What DBMS are you on? You could use WITH. But this does not exist on MYSQL.
with wo as
(select location as sfunction, order_number
from work_orders
union location, order_number
from work_orders_archived)
select sfunction,
count(*)
SUM(Laborhours) AS sumLaborHours,
SUM(LaborCost) AS sumLaborCost,
SUM(MaterialCost*MaterialQuanity) AS sumMaterialCost
from wo
LEFT OUTER JOIN
(SELECT HoursWorked AS Laborhours, TotalDollars AS LaborCost, WorkOrderNo
FROM LaborDetail) AS LD
ON COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = LD.WorkOrderNo
LEFT OUTER JOIN
(SELECT UnitCost AS MaterialCost, Qty AS MaterialQuanity, OrderNumber
FROM WorkOrderInventory) AS WOI
ON COALESCE(work_orders.order_number, Work_Orders_Archived.order_number) = WOI.OrderNumber
where wo.order_number = '919630'
group by sfunction
order by sfunction

Answer 3

The best guess is that the work orders appear more than once in one of the tables. Try these queries to check for duplicates in the two most obvious candidate tables:
select cnt, COUNT(*), MIN(order_number), MAX(order_number)
from (select order_number, COUNT(*) as cnt
from work_orders
group by order_number
) t
group by cnt
order by 1;
select cnt, COUNT(*), MIN(order_number), MAX(order_number)
from (select order_number, COUNT(*) as cnt
from work_orders_archived
group by order_number
) t
group by cnt
order by 1;
If either returns a row where cnt is not 1, then you have duplicates in the tables.