How to select every Monday date and every Friday date in the year - sql

Question

basically I want to be able to select monday and friday for every week in the year.
So for example this week coming i want 9/29/2014 and 10/3/2014, but i want this for every week in the year.

Answer 1

Here's one way (you might need to check which day of the week is setup to be the first, here I have Sunday as the first day of the week)
You can use a table with many rows (more than 365) to CROSS JOIN to in order to get a run of dates (a tally table).
My sys columns has over 800 rows in, you could use any other table or even CROSS JOIN a table onto itself to multiply up the number of rows
Here I used the row_number function to get a running count of rows and incremented the date by 1 day for each row:
select
dateadd(d, row_number() over (order by name), cast('31 Dec 2013' as datetime)) as dt
from sys.columns a
With the result set of dates now, it's trivial to check the day of week using datepart()
SELECT
dt,
datename(dw, dt)
FROM
(
select
dateadd(d, row_number() over (order by name), cast('31 Dec 2013' as datetime)) as dt
from
sys.columns a
) as dates
WHERE
(datepart(dw, dates.dt) = 2 OR datepart(dw, dates.dt) = 6)
AND dt >= '01 Jan 2014' AND dt < '01 Jan 2015'
Edit:
Here's an example SqlFiddle
http://sqlfiddle.com/#!6/d41d8/21757
Edit 2:
If you want them on the same row, days of the week at least are constant, you know Friday is always 4 days after Monday so do the same but only look for Mondays, then just add 4 days to the Monday...
SELECT
dt as MonDate,
datename(dw, dt) as MonDateName,
dateadd(d, 4, dt) as FriDate,
datename(dw, dateadd(d, 4, dt)) as FriDateName
FROM
(
select
dateadd(d, row_number() over (order by name), cast('31 Dec 2013' as datetime)) as dt
from
sys.columns a
) as dates
WHERE
datepart(dw, dates.dt) = 2
AND dt >= '01 Jan 2014' AND dt < '01 Jan 2015'
AND dt >= '01 Jan 2014' AND dt < '01 Jan 2015'
Example SqlFiddle for this:
http://sqlfiddle.com/#!6/d41d8/21764
(note that only a few rows come back because sys.columns is quite small on the SqlFiddle server, try another system table if this is a problem)

Answer 2

You can use a suitable table with numbers, like the master..spt_values table as basis for the range generation:
;WITH dates AS (
SELECT DATEADD(DAY,number,CAST('2014-01-01' AS DATE)) d
FROM master..spt_values WHERE TYPE = 'p'
AND number < 366
)
SELECT
Week = DATEPART(WEEK, d),
DayOfWeek = DATENAME(dw, d),
Date = d
FROM dates
WHERE DATENAME(dw, d) IN ('Monday', 'Friday')
-- or use datepart instead as datename might be specific to language
-- WHERE DATEPART(dw, d) IN (2,6)
Sample output:
Week DayOfWeek Date
----------- ------------------------------ ----------
1 Friday 2014-01-03
2 Monday 2014-01-06
2 Friday 2014-01-10
3 Monday 2014-01-13
3 Friday 2014-01-17
4 Monday 2014-01-20
4 Friday 2014-01-24
5 Monday 2014-01-27
5 Friday 2014-01-31

Answer 3

SELECT extract(isodow from "date_source") as datee 1-monday 7-sunday
and then in WHERE write datee IN ('1','2'....)