How do I calculate multiple sums and averages in a single query? - sql

Question

I am in a SQL class and struggling with one of the questions. We are using the AdventureWorksDW2014 database in SQL Server and this is the problem I'm stuck on:
Write a query that will return the employee key, first name, middle name, last name, total sales, and average amount per sale for every employee who has made sales to resellers. All monetary values should be rounded to two decimal places. Names should appear as a single record as "Last, First Middle." Sort the results by total sales (highest first), then by average amount per sale (highest first), then by employee name.
I have no problem selecting the EmployeeKey, nor with using concat and formatting the name as instructed. After exploring the data, it is clear that the employee information will need to come from the DimEmployee table, and the sales figures will need to come from the FactResellerSales table, and I am able to complete the inner join between the tables with no problem. I also know how to use the sum and avg functions to calculate the totals and averages for the employees individually, but those will only calculate for one employee at a time and only returns a single result. The part that I'm hung up on is creating the columns for the calculated sums and averages for each employee. The result I need to come up with needs to have a single column that shows the total sales of each employee and a single column that shows the average amount per sales for each employee, along with other information requested for each employee. So far, I have run
select distinct EmployeeKey
from FactResellerSales
to determine which employee keys are associated with sales, and it shows that there are 17. I attempted to construct the query using a subquery for each employee in the from statement,
(select EmployeeKey, sum (SalesAmount) as TotalSalesByEmp, avg (SalesAmount)
as AvgPerSaleByEmp
from FactResellerSales
where EmployeeKey = 272)
thinking that, even though it would be time consuming to do 17 subqueries, I could ultimately draw the requested data from them into the main query, but I get an error message of "Msg 8120, Level 16, State 1, Line 359
Column 'FactResellerSales.EmployeeKey' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause" when I try to test the subquery. But I can't leave out the EmployeeKey as I need it for the linking field of the inner join. My query so far (including the aliases I will use for the other fields as appropriate in the order by statement) is:
USE AdventureWorksDW2014
select e.EmployeeKey,
concat (e.LastName, ', ' + e.FirstName, ' ' + e.MiddleName) as EmployeeName
from FactResellerSales as s
inner join DimEmployee as e
on s.EmployeeKey = e.EmployeeKey
order by TotalSalesByEmp desc, AvgPerSaleByEmp desc, EmployeeName
I just need to figure out how to add the other two fields.
I've already described what the results I need should look like, but since that is apparently not good enough for some people, I will try to give an example. Apologies if the formatting is weird in the transition (I promise it looks right as I'm typing it).
| EmployeeKey | EmployeeName | TotalSalesByEmp | AvgPerSaleByEmp |
| 282 | Mitchell, Linda C | 10367007.43 | 1458.70 |
| 283 | Carson, Jillian | 10065803.54 | 1286.36 |
| 281 | Blythe, Michael G | 9293903.01 | 1314.74 |
| 272 | Jiang, Stephen Y | 1092123.86 | 1378.94 |
Please help.

Answer 1

Simply run your aggregation with GROUP BY on employee details which will calculate the total and average reseller sales across all 17 employees:
USE AdventureWorksDW2014
select e.EmployeeKey,
concat(e.LastName, ', ' + e.FirstName, ' ' + e.MiddleName) as EmployeeName,
sum(s.SalesAmount) as TotalSalesByEmp,
avg(s.SalesAmount) as AvgPerSaleByEmp
from FactResellerSales as s
inner join DimEmployee as e
on s.EmployeeKey = e.EmployeeKey
group by e.EmployeeKey,
e.LastName,
e.FirstName,
e.MiddleName
order by TotalSalesByEmp desc,
AvgPerSaleByEmp desc,
EmployeeName