Calculating Daily Change and New Salespersons - sql

Question

I have a SALES table with Person, Date and Qty:
Person Date Qty
Bob 2016-08-01 5
Bob 2016-08-02 2
Bob 2016-08-03 6
Bob 2016-08-04 4
Jim 2016-08-01 1
Jim 2016-08-02 3
Jim 2016-08-03 2
Jim 2016-08-04 2
Sheila 2016-08-03 9
Sheila 2016-08-04 12
I would like to produce 3 outputs
1) The Daily change in total Qty for the Persons who were selling the prior day:
Date Qty Change Pct Change
2016-08-01 0 0 0.00
2016-08-02 5 -1 -16.66
2016-08-03 8 3 60.00
2016-08-04 18 1 5.88
Note that 8/1/16 is the first day in my dataset, so total = 0 since no SalesPerson was selling the prior day. Also note that Sheila started selling on 8/3, which means here 8/3 sales do not figure into the 8/3 qty or change. However, when determining the 8/4 change, Sheila's 8/3 sales of 9 units are used to determine the correct total change of 1 unite for 8/4.
2) I want to break out the totals for new SalesPersons each day on one line per day. If no new Salespersons are added, then the date would show zeros.
Date New Qty
2016-08-01 6
2016-08-02 0
2016-08-03 9
2016-08-04 0
Since 8/1 was the first day of selling for anyone, both sales for Bob and Jim are included in the New Qty of 6 for 8/1.
3) The final output shows detail for #2, such as the date that a new SalesPerson started selling and the quantity they sold on that day.
Date Person New Qty
2016-08-01 Bob 5
2016-08-01 Jim 1
2016-08-03 Sheila 9
Are these 3 outputs possible in SQL Server?

Answer 1

You can use LAG() if you are using sql server 2012 or above. You got the "change". You can figure out the rest.
Query #1:
SELECT
dt.DateVal,
SUM(CASE WHEN dt.PreviousQuota = 0 THEN 0 ELSE dt.PreviousQuotadd END) Change
FROM
(
SELECT
Id,
Person,
DateVal,
Qty,
LAG(Qty, 1,0) OVER ( PARTITION BY Person ORDER BY DateVal) AS PreviousQuota ,
LEAD(Qty, 1,0) OVER ( PARTITION BY Person ORDER BY DateVal) AS NextQuota ,
LAG(Qty, 1,0) OVER ( PARTITION BY Person ORDER BY DateVal) AS PreviousQuotad ,
(Qty - LAG(Qty, 1,0) OVER ( PARTITION BY Person ORDER BY DateVal)) AS PreviousQuotadd
FROM Table1
) AS dt
Here is the Fiddlle link.

Answer 2

I solved the following queries:
Query #2:
WITH CTE_1 AS
(Select DISTINCT Date FROM [master].[dbo].[Sales] GROUP BY Date)
, CTE_2 AS
(select Person,Date,ROW_NUMBER() OVER(Partition By Person Order By Date) as RowNum, SUM(Qty) as [PersonDailySum]
FROM [master].[dbo].[Sales]
GROUP BY Person,Date)
,CTE_3 AS(
SELECT T0.date, SUm([PersonDailySum]) As [New Qty]
FROM CTE_1 T0
LEFT JOIN CTE_2 T1
ON T0.Date = T1.date AND T1.RowNum = 1
GROUP BY T0.Date)
SELECT Date, ISNULL([New Qty],0) AS [New Qty] FROM CTE_3
Query #3
SELECT Date,Person,SUM([PersonDailySum]) AS [New Qty] FROM (
select Person,Date,ROW_NUMBER() OVER(Partition By Person Order By Date) as RowNum, SUM(Qty) as [PersonDailySum]
FROM [master].[dbo].[Sales]
GROUP BY Person,Date) T0
WHERE T0.RowNum = 1
GROUP BY Date,Person