loop dates and return weeks tsql - sql

Question

I am very new in SQL (started just 3 days back) and I got an issue and would hope someone is able to assist me.
I have a query that creates date loops to return me the week number based on the passed in dates. The idea here is to pass loop through the days, months and years and return me a week value. But because of these, I have been getting multiple entries of the same result.
For eg. I am getting:
period_wk_key period_yr_key period_week period_week_day period_week_full_desc
--------------- -------------- ------------ -------------- -----------------------
200001 2000 1 6 2000 WEEK 1
200001 2000 1 6 2000 WEEK 1
200001 2000 1 6 2000 WEEK 1
. . . . .
200002 2000 2 6 2000 WEEK 2
200002 2000 2 6 2000 WEEK 2
200002 2000 2 6 2000 WEEK 2
. . . . .
200003 2000 3 6 2000 WEEK 3
each period_wk_key is returning me 7 similar rows which is not what I wanted.
The ideal situation should be:
period_wk_key period_yr_key period_week period_week_day period_week_full_desc
--------------- -------------- ------------ -------------- -----------------------
200001 2000 1 6 2000 WEEK 1
200002 2000 2 6 2000 WEEK 2
200003 2000 3 6 2000 WEEK 3
200004 2000 4 6 2000 WEEK 4
I need to know a way to limit the number of output from a loop so that I can have distinct records instead of multiple similar rows. I have attached a code below. It maybe crap to many of you but this is just my 3rd day beginning scripting. Much thanks for any help rendered.
DECLARE #iStartYear INT
SET #iStartYear = 2000
DECLARE #iEndYear INT
SET #iEndYear = 2030
DECLARE #iMth INT
SET #iMth = 1
DECLARE #iDay INT
SET #iDay = 1
DECLARE #iWeek INT
`DECLARE #StartDate DATETIME
WHILE (#iStartYear <= #iEndYear)
BEGIN
WHILE (#iMth <= 12)
BEGIN
WHILE (#iDay <= DATEDIFF(DAY,DATEADD(DAY, 0, DATEADD(m, ((#iStartYear - 1900) * 12) + #iMth - 1, 0)),DATEADD(DAY, 0, DATEADD(m, ((#iStartYear - 1900) * 12) + #iMth, 0)))))
BEGIN `
SET #iWeek = (DATEPART(dy, CONVERT(DATETIME, CONVERT(VARCHAR(4), #iStartYear) + '/' + CONVERT(VARCHAR(2), #iMth) + '/' + CONVERT(VARCHAR(2), #iDay))) - 1) / 7 + 1;
INSERT INTO dim_period_week (period_wk_key, period_yr_key, period_week, period_week_full_desc,start_date, end_date, period_week_day)
VALUES (
(SELECT CASE WHEN #iWeek < 10 THEN
CAST((#iStartYear) AS VARCHAR) + '0' + CAST((#iWeek) AS VARCHAR)
ELSE
CAST((#iStartYear) AS VARCHAR)+ CAST((#iWeek) AS VARCHAR)
END),
#iStartYear,
(SELECT (DATEPART(dy, CONVERT(DATETIME, CONVERT(VARCHAR(4), #iStartYear) + '/' + CONVERT(VARCHAR(2), #iMth) + '/' + CONVERT(VARCHAR(2), #iDay))) - 1) / 7 + 1),
(SELECT CAST((#iStartYear) AS VARCHAR) + ' ' + 'WEEK' + ' ' + CAST((#iWeek) AS VARCHAR)),
(SELECT DATEADD(wk,#iWeek-1, DATEADD(yy,#iStartYear-1900,0))), --START DATE
(SELECT DATEADD(wk,#iWeek, DATEADD(yy,#iStartYear-1900,0)) -1), --END DATE
(SELECT DATEDIFF(DAY, DATEADD(wk,#iWeek-1, DATEADD(yy,#iStartYear-1900,0)), DATEADD(wk,#iWeek, DATEADD(yy,#iStartYear-1900,0)) -1))
)
`SET #iDay = #iDay + 1
END
SET #iDay = 1
SET #iMth = #iMth + 1
END
SET #iMth = 1
SET #iStartYear = #iStartYear + 1
END
`

Answer 1

You are looping every day, but never storing at the day level, so you are doing 7 times as many INSERTs as needed. Add the following just above your INSERT statement
IF DATEPART(weekday, CAST(CAST(#iStartYear * 10000 + #iMth * 100 + #iDay AS VARCHAR(8)) AS datetime)) = 1
INSERT INTO dim_period_week ...

Answer 2

Below is a set based approach using a numbers table.
IF OBJECT_ID('tempdb.dbo.#Numbers') IS NOT NULL DROP TABLE #Numbers
GO
DECLARE #startDate DATETIME = '20000101'
SELECT
(a.Number * 256) + b.Number AS Number
INTO #Numbers
FROM
(SELECT number FROM master..spt_values WHERE type = 'P' AND number <= 255) a (Number),
(SELECT number FROM master..spt_values WHERE type = 'P' AND number <= 255) b (Number)
WHERE
(a.Number * 256) + b.Number BETWEEN 0 AND 1617
SELECT
WeekKey = CAST(YEAR(DATEADD(day, N.Number * 7, #startDate)) * 100 + DATEPART(week, DATEADD(day, N.Number * 7, #startDate)) AS VARCHAR(10)),
TheYear = YEAR(DATEADD(day, N.Number * 7, #startDate)),
TheWeek = DATEPART(week, DATEADD(day, N.Number * 7, #startDate)),
TheWeekDay= DATEPART(weekday, DATEADD(day, N.Number * 7, #startDate)),
WeekDetail= DATENAME(year, DATEADD(day, N.Number * 7, #startDate)) + ' WEEK ' + DATENAME(week, DATEADD(day, N.Number * 7, #startDate)),
StartDate = DATEADD(day, N.Number * 7, #startDate),
EndDate = DATEADD(day, 6, DATEADD(day, N.Number * 7, #startDate))
FROM #Numbers N
ORDER BY 1