Calendar showing null when date begins in previous year - sql

Question

This is the syntax I am using to create my calendar. The issue that I have is that since the startdate of Week1 is in 2012, startdate is showing as null. Is there a way to have the startdate (or enddate in other instances) populate even when it is in a different year? #Winds Of Change ---
That adds in a start date and end date where previously it was null. But what I am after is for example, I need my date range to run Sat - Wed. So let's take week 53 for 2013. The date range should be 12/28/2013 -- 01/01/14. Is there a way to tinker the calander into displaying in that format?
CREATE TABLE dbo.Calendar (
CalendarYear INT NOT NULL,
CalendarWeek INT NOT NULL,
WeekStartDate VARCHAR(50),
WeekEndDate VARCHAR(50),
CONSTRAINT PK_Calendar PRIMARY KEY (
CalendarYear,
CalendarWeek
)
)
SET DATEFIRST 6
DECLARE #StartDate DATETIME,
#NumOfDays INT
SET #StartDate = '20130101'
SET #NumOfDays = 1000;
WITH calendar
AS (
SELECT TOP (#NumOfDays) dateadd(day, row_number() OVER (
ORDER BY sc1.column_id
) - 1, #StartDate) AS CalendarDate
FROM sys.columns sc1
CROSS JOIN sys.columns sc2
)
INSERT INTO dbo.Calendar (
CalendarYear,
CalendarWeek,
WeekStartDate,
WeekEndDate
)
SELECT DATEPART(year, c.CalendarDate) AS Year,
convert(VARCHAR(100), DATEPART(week, c.CalendarDate)) AS Week, --DATEPART(week, c.CalendarDate) AS Week,
MAX(CASE DATEPART(WEEKDAY, c.CalendarDate)
WHEN 1
THEN convert(VARCHAR(50), c.CalendarDate, 101)
ELSE NULL
END) AS StartDate,
MAX(CASE DATEPART(WEEKDAY, c.CalendarDate)
WHEN 7
THEN convert(VARCHAR(50), c.CalendarDate, 101)
ELSE NULL
END) AS EndDate
FROM calendar c
GROUP BY DATEPART(year, c.CalendarDate),
DATEPART(Week, c.CalendarDate)
ORDER BY Year,
startdate,
convert(VARCHAR(100), DATEPART(week, c.CalendarDate)) --Week
SELECT *
FROM dbo.Calendar

Answer 1

So your problem is is that you're grouping by week and year, but at the beginning/end of the year, the year begins/ends on a different week. So if the first week starts on Wednesday, it's only a 3 day week for that Year.
I've had a small tinker, and I've got it working so that it displays the first/last day of the year as the start/end date of the week, by changing things around. Here is my modified version:
SELECT
DATEPART(year, c.CalendarDate) AS Year,
convert(VARCHAR(100), DATEPART(week, c.CalendarDate)) AS Week, --DATEPART(week, c.CalendarDate) AS Week,
convert(VARCHAR(50), MIN(c.CalendarDate), 101) AS StartDate,
convert(VARCHAR(50), MAX(c.CalendarDate), 101) AS EndDate
FROM
calendar c
GROUP BY
DATEPART(year, c.CalendarDate),
DATEPART(Week, c.CalendarDate)
ORDER BY
Year,
startdate,
convert(VARCHAR(100), DATEPART(week, c.CalendarDate)) --Week
Hope this helps.
EDIT: In response to your comment/edit, have a look at these update statements. Put them after your insert.
EDIT2: Don't use the above insert as well as the updates.
update dbo.Calendar set WeekStartDate = convert(VARCHAR(50), dateadd(day, 1, dateadd(week, -1, cast(WeekEndDate as datetime))), 101)
where WeekStartdate is null
update dbo.Calendar set WeekEndDate = convert(VARCHAR(50), dateadd(day, -1, dateadd(week, 1, WeekStartDate)), 101)
where WeekEndDate is null