Show only row with highest value - sql

Question

In my query I'm returning number of days a week something occurs. Everything is working fine, with the exception that I'm getting multiple rows returned where I only need the highest. So for example in my query, if the TotalDays is 3, I have a row for 1, 2 and 3. If its 4 then I have rows for 1,2,3 and 4, etc. What do I need to do so that I only get the highest one? I tried using both ROW_NUMBER and MAX but can't seem to figure out how to accomplish this with the CASES.
SELECT Employees.CustomerID, X.*, Customers.ReportID
FROM
(
SELECT
CASE WHEN [M] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Tu] = '1' THEN 1 ELSE 0 END +
CASE WHEN [W] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Th] = '1' THEN 1 ELSE 0 END +
CASE WHEN [F] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Sa] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Su] = '1' THEN 1 ELSE 0 END AS DaysofWeek
FROM
Customers
) X, Employees INNER JOIN ON Employees.EmployeesID = Customers.EmployeesID
GROUP BY Employees.CustomerID, Customers.ReportID, X.DaysofWeek
Few more details on this. For any given EmployeeID there can be unlimited ReportIDs and I want to return all of them but ONLY for where the DaysofWeek is the highest.
So EmployeeID 200 may have report 1001 and 1002 that are returned 2 days a week each. What should shows is
200 2 1001
200 2 1002
However, what is currently showing is:
200 1 1001
200 2 1001
200 1 1002
200 2 1002
Modified the query and added a couple more tables though everything is returning a value of 5.
WITH sub AS(
SELECT Shift1.EmployeeID, X.*, Schedule.Services, Schedule.ReportID
FROM
(
SELECT
CASE WHEN [M] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Tu] = '1' THEN 1 ELSE 0 END +
CASE WHEN [W] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Th] = '1' THEN 1 ELSE 0 END +
CASE WHEN [F] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Sa] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Su] = '1' THEN 1 ELSE 0 END AS DaysofWeek
FROM
Schedule
) X, Shift1 INNER JOIN (Shift2 INNER JOIN Schedule ON Shift2.Shift2ID = Schedule.Shift2ID) ON Shift1.Shift1ID = Shift2.Shift1ID
GROUP BY Shift1.EmployeeID, Schedule.Services, Schedule.ReportID, X.DaysofWeek
)
SELECT X.*
FROM sub X
JOIN (SELECT EmployeeID, ReportID, MAX(DaysofWeek) AS DaysofWeek
FROM sub
GROUP BY EmployeeID, ReportID) Y
ON X.DaysofWeek = Y.DaysofWeek
and X.EmployeeID = Y.EmployeeID
and X.ReportID = Y.ReportID

Answer 1

First, your query should look like:
SELECT e.CustomerID, c.DaysOfWeek, c.ReportId
FROM (SELECT c.*,
(CASE WHEN [M] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Tu] = '1' THEN 1 ELSE 0 END +
CASE WHEN [W] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Th] = '1' THEN 1 ELSE 0 END +
CASE WHEN [F] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Sa] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Su] = '1' THEN 1 ELSE 0 END
) AS DaysofWeek
FROM Customers c
) c JOIN
Employees e
ON e.EmployeesID = c.EmployeesID
GROUP BY e.CustomerID, c.ReportID, c.DaysofWeek;
I question the join (why would Employee.CustomerId not join to the Customers table?), but this is how you have it. To get the reports with the biggest day of the week, use DENSE_RANK():
SELECT e.CustomerID, c.DaysOfWeek, c.ReportId
FROM (SELECT c.*, DENSE_RANK() OVER (PARTITION BY c.EmployeesId ORDER BY DaysOfWeek DESC) as seqnum
FROM (SELECT c.*,
(CASE WHEN [M] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Tu] = '1' THEN 1 ELSE 0 END +
CASE WHEN [W] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Th] = '1' THEN 1 ELSE 0 END +
CASE WHEN [F] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Sa] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Su] = '1' THEN 1 ELSE 0 END
) AS DaysofWeek
FROM Customers c
) c
) c JOIN
Employees e
ON e.EmployeesID = c.EmployeesID
WHERE seqnum = 1
GROUP BY e.CustomerID, c.ReportID, c.DaysofWeek;

Answer 2

The query itself might be able to get cleaned a little better, however if your current query is working and showing you the output you've indicated, but you want to reduce it to what you indicate is your desired output, you should be able to use the with clause to do this as follows:
with sub as(
SELECT Employees.CustomerID, X.*, Customers.ReportID
FROM
(
SELECT
CASE WHEN [M] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Tu] = '1' THEN 1 ELSE 0 END +
CASE WHEN [W] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Th] = '1' THEN 1 ELSE 0 END +
CASE WHEN [F] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Sa] = '1' THEN 1 ELSE 0 END +
CASE WHEN [Su] = '1' THEN 1 ELSE 0 END AS DaysofWeek
FROM
Customers
) X INNER JOIN Employees ON Employees.EmployeesID = Customers.EmployeesID
GROUP BY Employees.CustomerID, Customers.ReportID, X.DaysofWeek
)
select x.*
from sub x
join (select customerid, reportid, max(daysofweek) as daysofweek
from sub
group by customerid, reportid) y
on x.daysofweek = y.daysofweek
and x.customerid = y.customerid
and x.reportid = y.reportid
Also your join clause was off.