SQL Server : how to use variable values from CTE in WHERE clause? - sql-server

Question

First of all please correct me if my title are not specific/clear enough.
I have use the following code to generate the start dates and end dates ：
DECLARE #start_date date, #end_date date;
SET #start_date = '2016-07-01';
with dates as
(
select
#start_date AS startDate,
DATEADD(DAY, 6, #start_date) AS endDate
union all
select
DATEADD(DAY, 7, startDate) AS startDate,
DATEADD(DAY, 7, endDate) AS endDate
from
dates
where
startDate < '2017-03-31'
)
select * from dates
Below is part of the output from above query ：
+------------+------------+
| startDate | endDate |
+------------+------------+
| 2016-07-01 | 2016-07-07 |
| 2016-07-08 | 2016-07-14 |
| 2016-07-15 | 2016-07-21 |
| 2016-07-22 | 2016-07-28 |
| 2016-07-29 | 2016-08-04 |
+------------+------------+
Now I have another table named sales, which have 3 columns sales_id,sales_date and sales_amount as below :
+----------+------------+--------------+
| sales_ID | sales_date | sales_amount |
+----------+------------+--------------+
| 1 | 2016-07-04 | 10 |
| 2 | 2016-07-06 | 20 |
| 3 | 2016-07-13 | 30 |
| 4 | 2016-07-19 | 15 |
| 5 | 2016-07-21 | 20 |
| 6 | 2016-07-25 | 25 |
| 7 | 2016-07-26 | 40 |
| 8 | 2016-07-29 | 20 |
| 9 | 2016-08-01 | 30 |
| 10 | 2016-08-02 | 30 |
| 11 | 2016-08-03 | 40 |
+----------+------------+--------------+
How can I create the query to show the total sales amount of each week (which is between each startDate and endDate from the first table)? I suppose I will need to use a recursive query with WHERE clause to check if the dates are in between startDate and endDate but I cant find a working example.
Here are my expected result (the startDate and endDate are the records from the first table) :
+------------+------------+--------------+
| startDate | endDate | sales_amount |
+------------+------------+--------------+
| 2016-07-01 | 2016-07-07 | 30 |
| 2016-07-08 | 2016-07-14 | 30 |
| 2016-07-15 | 2016-07-21 | 35 |
| 2016-07-22 | 2016-07-28 | 65 |
| 2016-07-29 | 2016-08-04 | 120 |
+------------+------------+--------------+
Thank you!

Answer 1

Your final Select (after the cte) should be something like this
Select D.*
,Sales_Amount = sum(Sales)
From dates D
Join Sales S on (S.sales_date between D.startDate and D.endDate)
Group By D.startDate,D.endDate
Order By D.startDate
EDIT: You could use a Left Join if you want to see missing dates from
Sales