SQL Server : get next relative day of week. (Next Monday, Tuesday, Wed…)

Question

What I need is a date for the next given day (Monday, Tuesday, Wed...) following today\'s date.

The user is allowed to select what day following they want and that i

Answer 1

It's an old question. But I'm sure that posting better solution worth it.

-- 0 = 1st Mon, 1 = 1st Tue, 2 = 1st Wed, ..., 5 = 1st Sat, 6 = 1st Sun
-- 7 = 2nd Mon, 8 = 2nd Tue, ...
declare @NextDayID int = 0, @Date date = getdate()

select cast (cast (
    -- last Monday before [Date] inclusive, starting from 1900-01-01
    datediff (day, @NextDayID % 7, @Date) / 7 * 7
    -- shift on required number of days
    + @NextDayID + 7
    as datetime) as date)

This solution is improved solution of @Bogdan Sahlean. It can operate @NextDayID that is greater than 6. So you can, for example, find 2nd Monday from today.

Following query shows that my solution works correctly.

select [Date]
    , convert (char(5), [0], 10) as Mon1
    , convert (char(5), [1], 10) as Tue1
    , convert (char(5), [2], 10) as Wed1
    , convert (char(5), [3], 10) as Thu1
    , convert (char(5), [4], 10) as Fri1
    , convert (char(5), [5], 10) as Sat1
    , convert (char(5), [6], 10) as Sun1
    , convert (char(5), [7], 10) as Mon2
    , convert (char(5), [8], 10) as Tue2
from (
    select [Date], NextDayID
        , cast (cast (
          datediff (day, NextDayID % 7, [Date]) / 7 * 7 -- last Monday before [Date] inclusive, starting from 1900-01-01
        + NextDayID + 7 -- shift on required number of days
        as datetime) as date) as NextDay
    from (
        select datefromparts (2018, 5, dt) as [Date]
        from (values(14),(15),(16),(17),(18),(19),(20))t_(dt)
    ) d
    cross join (values(0),(1),(2),(3),(4),(5),(6),(7),(8))nd(NextDayID)
) t
pivot (
    min (NextDay) for NextDayID in ([0], [1], [2], [3], [4], [5], [6], [7], [8])
) pvt

Result:

Date       | Mon1  | Tue1  | Wed1  | Thu1  | Fri1  | Sat1  | Sun1  | Mon2  | Tue2
-----------+-------+-------+-------+-------+-------+-------+-------+-------+------
2018-05-14 | 05-21 | 05-15 | 05-16 | 05-17 | 05-18 | 05-19 | 05-20 | 05-28 | 05-22
2018-05-15 | 05-21 | 05-22 | 05-16 | 05-17 | 05-18 | 05-19 | 05-20 | 05-28 | 05-29
2018-05-16 | 05-21 | 05-22 | 05-23 | 05-17 | 05-18 | 05-19 | 05-20 | 05-28 | 05-29
2018-05-17 | 05-21 | 05-22 | 05-23 | 05-24 | 05-18 | 05-19 | 05-20 | 05-28 | 05-29
2018-05-18 | 05-21 | 05-22 | 05-23 | 05-24 | 05-25 | 05-19 | 05-20 | 05-28 | 05-29
2018-05-19 | 05-21 | 05-22 | 05-23 | 05-24 | 05-25 | 05-26 | 05-20 | 05-28 | 05-29
2018-05-20 | 05-21 | 05-22 | 05-23 | 05-24 | 05-25 | 05-26 | 05-27 | 05-28 | 05-29

This solution doesn't depend on @@datefirst.