select group by column optionally in rows - sql

Question

I need to calculate employee salaries.
I have a table and two views which holds data i need to perform a query, here are the tables
Employees_View
--------
ID Name PayRate PayUnit Commission
1 James 10 C 0
2 Mike 10000 S 0
3 Jude 20000 SC 5
4 Clara 8 C 0
When PayUnit is C (Commission) then PayRate is in Percent, this is percent of the total sale by this employee, whereas the Commission field is commission percent on total sales and its only for SC employees
Jobs
ID Created
1 2016-01-21 10:56:05
2 2016-01-21 10:56:05
3 2016-01-21 10:56:05
4 2016-01-21 10:56:05
5 2016-01-21 12:11:59
6 2016-01-25 08:03:07
7 2015-11-01 22:55:22
Jobs_Item_View
Job_ID Amount Emp_ID
1 135 4
1 500 2
3 1500 2
3 250 4
4 1000 2
5 500 4
6 500 4
7 500 1
PayUnits
Code Name
S Salary
C Commission
SC Salary plus Commission
Here is what i tried
SELECT
ev.PayRate,
ev.name AS Employee,
CASE ev.PayUnitCode WHEN 'C' THEN
SUM(jiv.Amount) - (SUM(jiv.Amount) * (ev.PayRate / 100))
WHEN 'SC' THEN
ev.payrate + SUM(jiv.Amount) - (SUM(jiv.Amount) * (ev.Commission / 100))
ELSE ev.payrate
END AS pay,
LEFT(DATENAME(month, j.Created), 3) + '-' + CAST(YEAR(j.Created) AS NVARCHAR) AS Month,
jiv.Emp_ID,
pu.Name AS PayUnit,
ev.Code, ev.Commission
FROM
dbo.Employees_View AS ev LEFT OUTER JOIN
dbo.Job_Items_View AS jiv ON jiv.Emp_ID = ev.ID LEFT OUTER JOIN
dbo.Jobs AS j ON j.ID = jiv.Job_ID LEFT OUTER JOIN
dbo.PayUnits AS pu ON pu.Code = ev.PayUnitCode
GROUP BY jiv.Emp_ID,
pu.Name,
ev.PayUnitCode,
ev.PayRate, ev.name,
LEFT(DATENAME(month, j.Created), 3) + '-' + CAST(YEAR(j.Created) AS NVARCHAR),
ev.Code, ev.Commission
This is what i got
Result
PayRate Employee pay Month Emp_ID PayUnit Commission
20000 Jude NULL NULL NULL Salary plus Commission 5.00
10 James 900 Nov-2015 1 Commission 0.00
8 Clara 2760 Jan-2016 4 Commission 0.00
10000 Mike 10000 Jan-2016 2 Salary 0.00
Expected Output
Result
PayRate Employee pay Month Emp_ID PayUnit Commission
20000 Jude 20241.75 Jan-2016 3 Salary plus Commission 5.00
10 James 900 Nov-2015 1 Commission 0.00
8 Clara 2760 Jan-2016 4 Commission 0.00
10000 Mike 10000 Jan-2016 2 Salary 0.00
the Pay for the SC employee isn't correct. it is suppose to be Salary (20000) plus 5% or total sales (4835) which is 241.75 - 20,241.75

Answer 1

The reason for the nulls is that one of the employees did not contribute to any jobs, so SUM(jiv.Amount) will always be null for them and any calculations involving that expression will also result in null. You can fix by doing ISNULL(SUM(jiv.Amount), 0). Similarly for the dates, they are also driven by the jobs data, but if an employee wasn't involved in any jobs they will be null also. ISNULL() could be used for these as well.
I've broken the problem down by using Common Table Expressions:
DECLARE #startDateTime DATETIME = '2016-01-01 00:00:00'
DECLARE #endDateTime DATETIME = '2016-01-31 23:59:59'
;WITH sales AS
(
SELECT
ev.ID,
ISNULL(SUM(jiv.Amount), 0) AS TotalSales,
MONTH(j.Created) AS [Month],
YEAR(j.Created) AS [Year]
FROM Employees_View AS ev
LEFT JOIN Job_Items_View AS jiv ON jiv.Emp_ID = ev.ID
LEFT JOIN Jobs AS j ON j.ID = jiv.Job_ID
WHERE j.Created BETWEEN #startDateTime AND #endDateTime
GROUP BY
ev.ID,
MONTH(j.Created),
YEAR(j.Created)
),
commissions AS
(
SELECT
s.ID,
CASE ev.PayUnitCode
WHEN 'C' THEN s.TotalSales * (ev.PayRate / 100)
WHEN 'SC' THEN (SELECT SUM(Amount) FROM Job_Items_View) * (ev.Commission / 100)
ELSE 0
END AS TotalCommission
FROM sales AS s
JOIN Employees_View AS ev ON ev.ID = s.ID
),
salaries AS
(
SELECT
ID,
CASE PayUnitCode
WHEN 'C' THEN 0
ELSE PayRate
END AS Salary
FROM Employees_View
),
totals AS
(
SELECT
salaries.ID,
ISNULL(sales.Month, MONTH(#startDateTime)) AS [Month],
ISNULL(sales.Year, YEAR(#startDateTime)) AS [Year],
ISNULL(sales.TotalSales, 0) AS TotalSales,
salaries.Salary,
ISNULL(commissions.TotalCommission, 0) AS TotalCommission
FROM salaries
LEFT JOIN sales ON salaries.ID = sales.ID
LEFT JOIN commissions ON commissions.ID = sales.ID
)
SELECT
ev.PayRate,
ev.Name,
t.Salary + t.TotalCommission AS Pay,
LEFT(DATENAME(MONTH, DATEADD(MONTH , t.[Month], -1)), 3)
+ '-' + CAST(t.[Year] AS VARCHAR) AS [Month],
ev.ID AS Emp_ID,
pu.Name AS PayUnit,
ev.Commission
FROM totals AS t
JOIN Employees_View AS ev ON ev.ID = t.ID
JOIN PayUnits AS pu ON pu.Code = ev.PayUnitCode
Click here to see it in action and have a play on SQL Fiddle.