Find last sunday

Question

How will you find last sunday of a month in sql 2000?

Answer 1

Next sunday in SQL, regardless which day is first day of week: returns 2011-01-02 23:59:59.000 on 22-dec-2010:

select DateADD(ss, -1, DATEADD(week, DATEDIFF(week, 0, getdate()), 14))

Answer 2

select next_day(last_day(sysdate)-7, 'Sunday') from dual

Answer 3

DECLARE @LastDateOfMonth smalldatetime
SELECT @LastDateOfMonth = DATEADD(month, DATEDIFF(month, -1, GETDATE()), 0) -1
Select DATEADD(dd,-( CASE WHEN DATEPART(weekday,@LastDateOfMonth) = 1 THEN 0 ELSE DATEPART(weekday,@LastDateOfMonth) - 1 END ),@LastDateOfMonth)

Answer 4

An alternative approach, borrowed from data warehousing practice. Create a date-dimension table and pre-load it for 10 years, or so.

TABLE dimDate (DateKey, FullDate, Day, Month, Year, DayOfWeek, 
               DayInEpoch, MonthName, LastDayInMonthIndicator, many more..)

The easiest way to fill-in the dimDate is to spend an afternoon with Excel and then import to DB from there. A half-decent dimDate table has 50+ columns -- anything you ever wanted to know about a date.

With this in place, the question becomes something like:

SELECT max(FullDate)
FROM dimDate
WHERE DayOfWeek = 'Sunday'
      AND Month = 11
      AND Year = 2009;

Essentially, all date related queries become simpler.

Answer 5

I find some of these solutions hard to understand so here's my version with variables to explain the steps.

ALTER FUNCTION dbo.fn_LastSundayInMonth
(
  @StartDate DATETIME
 ,@RequiredDayOfWeek INT    /* 1= Sunday */
)
RETURNS DATETIME
AS
/*
A detailed step by step way to get the answer...

SELECT dbo.fn_LastSundayInMonth(getdate()-31,1)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,2)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,3)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,4)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,5)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,6)
SELECT dbo.fn_LastSundayInMonth(getdate()-31,7)
*/
BEGIN
    DECLARE @MonthsSince1900 INTEGER
    DECLARE @NextMonth INTEGER
    DECLARE @DaysToSubtract INTEGER
    DECLARE @FirstDayOfNextMonth DATETIME
    DECLARE @LastDayOfMonthDayOfWeek INTEGER
    DECLARE @LastDayOfMonth DATETIME
    DECLARE @ReturnValue DATETIME

    SET @MonthsSince1900=DateDiff(month, 0, @StartDate)
    SET @NextMonth=@MonthsSince1900+1
    SET @FirstDayOfNextMonth = DateAdd(month,@NextMonth, 0)
    SET @LastDayOfMonth = DateAdd(day, -1, @FirstDayOfNextMonth)

    SET @ReturnValue = @LastDayOfMonth

    WHILE DATEPART(dw, @ReturnValue) <> @RequiredDayOfWeek
        BEGIN
            SET @ReturnValue = DATEADD(DAY,-1, @ReturnValue)
        END

    RETURN @ReturnValue
END

Answer 6

SELECT
 DATEADD(day,DATEDIFF(day,'19000107',DATEADD(month,DATEDIFF(MONTH,0,GETDATE() /*YourValuehere*/),30))/7*7,'19000107')

Edit: A correct, final, working answer from my colleague.