How to use recurring CTE for Time Series - sql

Question

I have a table which shows the following data
Called Declines
date
accountId
declineReason
04/10/22
1344
Not enough funds
05/10/22
1222
Incorrect Password
05/10/22
1677
timeout
06/10/22
1222
Incorrect Password
07/10/22
1677
timeout
07/10/22
1222
Incorrect Password
10/10/22
1677
timeout
11/10/22
1344
Incorrect Password
11/10/22
1222
Incorrect Password
12/10/22
1677
timeout
13/10/22
1222
Incorrect Password
15/10/22
1677
timeout
15/10/22
1222
Incorrect Password
17/10/22
1677
timeout
etc (note declineReasons may increase in terms of distinct values and is not limited to 3 shown)
what I would like to have as my final table is the below
WeekEnd
declineReason
CountOfReasonPerWeek
10/10/22
Not enough funds
1
10/10/22
Incorrect Password
3
10/10/22
timeout
3
17/10/22
Not enough funds
0
17/10/22
Incorrect Password
4
17/10/22
timeout
3
I have created the week loop and table which counts no. of total declines
WITH date_loop AS (
SELECT
CAST('2022-08-01' AS DATE) AS WeekEnd,
CAST('2022-08-02' AS DATE) AS BeforeDate,
CAST('2022-07-25' AS DATE) AS AfterDate
UNION ALL
SELECT
DATEADD(ww, 1, WeekEnd),
DATEADD(ww, 1, BeforeDate),
DATEADD(ww, 1, AfterDate)
FROM date_loop
WHERE BeforeDate < DATEADD(ww, -1, GETDATE())
),
CountOfDDeclineByReasonAllTime AS (
SELECT
count(*) AS totalDeclinesPerReasonCode
FROM
Declines
GROUP BY
declineReason),
But I am unsure how I can use a correlated subquery to get values returned in the format as desired, if anyone has any pointers that would be great

Answer 1

data
CREATE TABLE Declines(
date VARCHAR(100) NOT NULL
,accountId INTEGER NOT NULL
,declineReason VARCHAR(100) NOT NULL
);
INSERT INTO Declines
(date,accountId,declineReason) VALUES
('04/10/22',1344,'Not enough funds'),
('05/10/22',1222,'Incorrect Password'),
('05/10/22',1677,'timeout'),
('06/10/22',1222,'Incorrect Password'),
('07/10/22',1677,'timeout'),
('07/10/22',1222,'Incorrect Password'),
('10/10/22',1677,'timeout'),
('11/10/22',1344,'Incorrect Password'),
('11/10/22',1222,'Incorrect Password'),
('12/10/22',1677,'timeout'),
('13/10/22',1222,'Incorrect Password'),
('15/10/22',1677,'timeout'),
('15/10/22',1222,'Incorrect Password'),
('17/10/22',1677,'timeout');
query
first since your value is not date change to date by using Convert(date, column, 3)
second get the last day of week by using
DATEADD(dd, 7-(DATEPART(dw, column)), column) as WeekEnd
third use Subquery to have better understanding of using Count function
select WeekEnd,
       declineReason,
       Count(declineReason) CountOfReasonPerWeek
from   (select Dateadd(dd, 7 - ( Datepart(dw, Convert(date, date, 3)) ),
                      Convert(date, date, 3)
               ) WeekEnd,
               declineReason
        from   Declines) a
group  by declineReason,
          WeekEnd
dbfiddle