how to get last week count using sql statement? - sql

Question

I'm trying to write a sql query to get last week's count in the format of mm/count/yyyy. In my situation, Wednesday starts a new week. So today March 8th, 2012 is the second week of March, and the last week count is 03/01/2012. Please note, the 01 means week count not date. If consider March 1st, 2012, the last week count should be the last week of Feburary which is 02/05/2012
Update: Thanks for Steve's comment, reminding me to clear my question here. Each month starts from it's first Wednesday. So the 03/01/2012 starts from March 7th, 2012 to March 13th, 2012
Any sql query solution?
I'm using sql-server

Answer 1

Here's some date logic to get you started. I can't comprehend your funky "last week count" definition by the two examples, so I can't code it.
DECLARE
#Now datetime,
#Today datetime,
#MonthStart datetime,
#WeekCount int,
#Result varchar(10)
SET #Now = GetDate()
SET #Today = DateAdd(dd, DateDiff(dd, 0, #Now), 0)
SET #MonthStart = DateAdd(mm, DateDiff(mm, 0, #Today), 0)
-- relative to the actual day the month started
SET #WeekCount = ((DatePart(dd, #Today)-1) / 7) + 1
-- relative to Sunday
--SET #WeekCount = (DatePart(week, #Today) - (DatePart(week, #MonthStart) + 1
SET #Result = convert(varchar(10), #Today, 101)
SET #Result =
LEFT(#Result, 3) -- month/
+ RIGHT('z00' + convert(varchar(2), #WeekCount), 2) -- week with zero pad
+ RIGHT(#Result, 5) -- /year
SELECT
#Now as TheNow,
#Today as Today,
#MonthStart as MonthStart,
#WeekCount as WeekCount,
#Result as Result
See also SET DATEFIRST

Answer 2

in oracle:
select to_char( sysdate, 'w' ) from dual

Answer 3

#Steven,
Sorry, this didn't fit as a comment.
Your description of "[nth] week in [month]" is not clear. Your week starts on Wednesday. February first was a Wednesday, so the weeks in February, 2012, if there are indeed 5 of them, are
February 1-7
February 8-14
February 15-21
February 22-28 and
February 29 - March 6
You describe March 8 as being in the "second week of March," so the first week of March must be the previous week, which is February 29 - March 6. Note that this is also what you call "the last (fifth) week in February."
By your description, then, the weeks you write as '02/05/2012' and '03/01/2012' are the same week with different names.
What is the rule that lets you know that
You want the same "last week" when you run the program March 1 as when you run it March 8
You want that week (which is the same) described differently in these two cases.
Or does your question have a mistake in it.
Once you can describe what you need, it will be easy to program. If you don't know what you want, it will be impossible to program.

Answer 4

In SQL Server these queries return 1,1,2,5
select ((DATEPART(dd, 'March 01, 2012')-1)/7) + 1
select ((DATEPART(dd, 'March 07, 2012')-1)/7) + 1
select ((DATEPART(dd, 'March 08, 2012')-1)/7) + 1
select ((DATEPART(dd, 'March 31, 2012')-1)/7) + 1
So this may be what you need
declare #dt datetime = 'March 31, 2012'
select
CONVERT(nvarchar(4), DATEPART(month,#dt)) + '/' +
CONVERT(nvarchar(4), ((DATEPART(dd, #dt)-1)/7) + 1) + '/' +
CONVERT(nvarchar(4), DATEPART(year,#dt))
which produces '3/5/2012'

Answer 5

SELECT
RIGHT(100 + MONTH(D) , 2) + '/' +
RIGHT(100 + (DAY(D) + 6) / 7, 2) + '/' +
DATENAME(YEAR, D)
FROM (
SELECT DATEADD(WEEK, -1, GETDATE()) AS D
) s

Answer 6

I think that should do it, I don't get the value for last week because it was confusing and the answer is cleaner that way, you can just add a DATEADD(day,-7,date) somewhere.
SET DATEFORMAT YDM
CREATE TABLE #Dates (Date DATETIME)
INSERT INTO #Dates VALUES ('2012-31-03');
INSERT INTO #Dates VALUES ('2012-15-02');
INSERT INTO #Dates VALUES ('2012-02-04');
INSERT INTO #Dates VALUES ('2012-02-05');
WITH Mondays as (
SELECT DATEADD(week, DATEDIFF(week,0, DATEADD(day,6-DATEPART(day,d.Date),d.Date) ), 0) FirstMonday,
DATEADD(week, DATEDIFF(week,0, DATEADD(day,6-DATEPART(day,DATEADD(month, -1, d.Date)),DATEADD(month, -1, d.Date)) ), 0) FirstMondayOfLastMonth,
d.Date
FROM #Dates d),
Wednesday as (
SELECT CASE WHEN DATEPART(day,m.FirstMonday) <= 5
THEN DATEADD(day,2,m.FirstMonday)
ELSE DATEADD(day,-5,m.FirstMonday) END FirstWednesday,
CASE WHEN DATEPART(day,m.FirstMondayOfLastMonth) <= 5
THEN DATEADD(day,2,m.FirstMondayOfLastMonth)
ELSE DATEADD(day,-5,m.FirstMondayOfLastMonth) END FirstWednesdayOfLastMonth,
m.Date
FROM Mondays m)
SELECT w.Date,
CASE WHEN w.Date >= w.FirstWednesday THEN
RIGHT('0' + CAST(DATEPART(month,w.Date) AS NVARCHAR(2)),2)
+ '/0' + CAST(DATEDIFF(week,w.FirstWednesday, w.Date) + 1 AS NVARCHAR(2))
+ '/' + CAST(DATEPART(year,w.Date) AS NVARCHAR(4))
ELSE
RIGHT('0' + CAST(DATEPART(month,w.FirstWednesdayOfLastMonth) AS NVARCHAR(2)),2)
+ '/0' + CAST(DATEDIFF(week,w.FirstWednesdayOfLastMonth, w.Date) + 1 AS NVARCHAR(2))
+ '/' + CAST(DATEPART(year,w.FirstWednesdayOfLastMonth) AS NVARCHAR(4))
END AS weekDate
FROM Wednesday w
DROP TABLE #Dates
The result is :
Date weekDate
2012-03-31 00:00:00.000 03/04/2012
2012-02-15 00:00:00.000 02/03/2012
2012-04-02 00:00:00.000 03/05/2012
2012-05-02 00:00:00.000 05/01/2012