Get the week start date and week end date from wee

Question

I have a query that counts member's wedding dates in the database...

Select 
  Sum(NumberOfBrides) As [Wedding Count], 
  DATEPART( wk, WeddingDate) as [Week Number],
  DATEPART( year, WeddingDate) as [Year]
FROM  MemberWeddingDates
Group By DATEPART( year, WeddingDate), DATEPART( wk, WeddingDate)
Order By Sum(NumberOfBrides) Desc

How do I work out when the start and end of each week represented in the result set?

Select 
      Sum(NumberOfBrides) As [Wedding Count], 
      DATEPART( wk, WeddingDate) as [Week Number],
      DATEPART( year, WeddingDate) as [Year],
      ??? as WeekStart,
      ??? as WeekEnd

    FROM  MemberWeddingDates
    Group By DATEPART( year, WeddingDate), DATEPART( wk, WeddingDate)
    Order By Sum(NumberOfBrides) Desc

Answer 1

The most voted answer works fine except for the 1st week and last week of a year. For example, if the value of WeddingDate is '2016-01-01', the result will be 2015-12-27 and 2016-01-02, but the right answer is 2016-01-01 and 2016-01-02.

Try this:

Select 
  Sum(NumberOfBrides) As [Wedding Count], 
  DATEPART( wk, WeddingDate) as [Week Number],
  DATEPART( year, WeddingDate) as [Year],
  MAX(CASE WHEN DATEPART(WEEK, WeddingDate) = 1 THEN CAST(DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate), 0) AS date) ELSE DATEADD(DAY, 7 * DATEPART(WEEK, WeddingDate), DATEADD(DAY, -(DATEPART(WEEKDAY, DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate), 0)) + 6), DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate), 0))) END) as WeekStart,
  MAX(CASE WHEN DATEPART(WEEK, WeddingDate) = DATEPART(WEEK, DATEADD(DAY, -1, DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate) + 1, 0))) THEN DATEADD(DAY, -1, DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate) + 1, 0)) ELSE DATEADD(DAY, 7 * DATEPART(WEEK, WeddingDate) + 6, DATEADD(DAY, -(DATEPART(WEEKDAY, DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate), 0)) + 6), DATEADD(YEAR, DATEDIFF(YEAR, 0, WeddingDate), 0))) END) as WeekEnd
FROM  MemberWeddingDates
Group By DATEPART( year, WeddingDate), DATEPART( wk, WeddingDate)
Order By Sum(NumberOfBrides) Desc;

The result looks like:

It works for all weeks, 1st or others.