title: Get the week start date and week end date from week number
body: <p>I have a query that counts member's wedding dates in the database.</p>
  <pre><code>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
  </code></pre>
  <p>How do I work out when the start and end of each week represented in the result set?</p>
  <pre><code>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
  </code></pre>