CTE : looping data input every 15 days| SQL, SQL SERVER - sql

Question

I have this test code from the guides here that I modified for test practice.
What I'm trying to achieve in this code is for it to loop the input based on a certain number, and it will loop with a 15 day gap.
Scenario: I will set the looping into 5 times. And the start date of the loop is 08/15/2019
So, the data that should be inputted is 08/15/2019, 08/30/2019, 09/15/2019, 09/30/2019, 10/15/2019 (Assuming that all dates are in 30 days.)
DECLARE #MYTESTTABLE TABLE ([Month] date, [Data 1] INT, [Data 2] INT, [Data 3] INT);
WITH MYLOOP AS (
SELECT CAST('2019-01-01' AS DATE) AS [date], 100 as [Data 3]
UNION ALL
SELECT DATEADD(MONTH, 1, [date]), [Data 3]=[Data 3]+1
FROM MYLOOP
WHERE DATEADD(MONTH, 1, [date]) < CAST('2022-01-01' AS DATE) )
INSERT INTO #MYTESTTABLE ([Month], [Data 1], [Data 2], [Data 3])
SELECT LEFT([date],10) as [Month], 100 AS [Data 1], 100 AS [Data 2], [Data 3]
FROM MYLOOP
SELECT * FROM #MYTESTTABLE
This is the guide that I got based on that scenario.
My problem now is that I'm having a hard time implementing the 2 SQL Queries into 1.
DECLARE #YourTable table (YourDate int, valuex int,tests int)
insert into #YourTable VALUES ('100',5,11)
;WITH AllNumbers AS
(SELECT 1 AS Number, 100 AS [value]
UNION ALL
SELECT Number+1, [value]=[value]+1
FROM AllNumbers
WHERE Number<=15-1 )
SELECT
YourDate, valuex, tests
FROM #YourTable y
INNER JOIN AllNumbers a ON 1=1
This is what I got so far.
DECLARE #MYTESTTABLE TABLE ([Month] date, [Data 1] INT, [Data 2] INT, [Data 3] INT);
WITH MYLOOP AS (
SELECT CAST('2019-01-01' AS DATE) AS [date], 1 as [Data 2], 100 as [Data 3]
UNION ALL
SELECT DATEADD(MONTH, 1, [date]), [Data 2]+1, [Data 3]=[Data 3]+1
FROM MYLOOP
WHERE [Data 2] < 7 )
INSERT INTO #MYTESTTABLE ([Month], [Data 1], [Data 2], [Data 3])
SELECT LEFT([date],10) as [Month], 100 AS [Data 1], [Data 2], [Data 3]
FROM MYLOOP
SELECT * FROM #MYTESTTABLE
How do is set to to trigger, or add every 15 days, and not every 1 month(30 days)?
May I ask for your assistance on this matter?

Answer 1

If you are looking for 5 dates only from your input date, this following script will work-
Input date must need to be 15 or 30 of a month
DECLARE #st_dt DATE = '08/15/2019'
DECLARE #prev_dt DATE
DECLARE #LC INT =0
DECLARE #MYTESTTABLE TABLE ([Month] date)
WHILE #LC < 5
BEGIN
IF #LC = 0
BEGIN
INSERT INTO #MYTESTTABLE ([Month]) VALUES(#st_dt)
SET #prev_dt = #st_dt
END
ELSE
BEGIN
IF DATEPART(DD,#prev_dt) = 15
BEGIN
INSERT INTO #MYTESTTABLE ([Month]) VALUES(DATEADD(DD,(CASE WHEN DATEPART(MM,#prev_dt) = 2 THEN 13 ELSE 15 END) ,#prev_dt))
SET #prev_dt = DATEADD(DD,(CASE WHEN DATEPART(MM,#prev_dt) = 2 THEN 13 ELSE 15 END) ,#prev_dt)
END
ELSE
BEGIN
INSERT INTO #MYTESTTABLE ([Month])
VALUES(DATEADD(DD,(15-DATEPART(DD,DATEADD(MM,1,#prev_dt))),DATEADD(MM,1,#prev_dt)))
SET #prev_dt = DATEADD(DD,(15-DATEPART(DD,DATEADD(MM,1,#prev_dt))),DATEADD(MM,1,#prev_dt))
END
END
SET #LC = #LC + 1
END
SELECT * FROM #MYTESTTABLE
Output is-
Month
2019-08-15
2019-08-30
2019-09-15
2019-09-30
2019-10-15
Now, If only adding +15 days with previous date can satisfy your requirement, this is easy and this following script will work for you-
DECLARE #st_dt DATE = '8/01/2019'
DECLARE #prev_dt DATE
DECLARE #LC INT =0
DECLARE #MYTESTTABLE TABLE ([Month] date)
WHILE #LC < 5
BEGIN
IF #LC = 0
BEGIN
INSERT INTO #MYTESTTABLE ([Month]) VALUES(#st_dt)
SET #prev_dt = #st_dt
END
ELSE
BEGIN
INSERT INTO #MYTESTTABLE ([Month]) VALUES(DATEADD(DD,15,#prev_dt))
SET #prev_dt = DATEADD(DD,15,#prev_dt)
END
SET #LC = #LC + 1
END
SELECT * FROM #MYTESTTABLE

Answer 2

This is the CTE version
-- straight 15 days addition
declare #startdate date = '2019-08-15'
declare #loop smallint = 15
;with cte_count as (
select 0 ctr
union all
select ctr + 1 from cte_count
where ctr < #loop-1
)
select dateadd(day,ctr*15,x.newdate) [Date] from cte_count
cross join
(select #startdate newdate) x
--- below shows 15th day and end of month
declare #startdate date = '2019-08-15'
declare #loop smallint = 50
;with cte_count as (
select 0 ctr
union all
select ctr + 1 from cte_count
where ctr < #loop-1
)
select
distinct
cast(iif(day(dateadd(day,ctr*15,newdate))<=15,
dateadd(day,14,DATEADD(m, DATEDIFF(m, 0, eomonth(dateadd(day,ctr*15,newdate))), 0))
,eomonth(dateadd(day,ctr*15,newdate))) as date)
from cte_count
cross join
(select #startdate newdate) x