SQL Query - Have to determine if it is a specific day of the month (ex: 2 Tuesday of month) - sql

Question

I have an app that allows users schedule an action to occur in the future. For example, that can select a date and schedule it to run on that day every month (ex: the 15th of each month). However, I now need to allow them to select a week day and week of the month. For example, they need to run an action the first friday of the month. Therefore I am allowing the to select the weekday (monday, tuesday, wednesday....) and week of the month (1st, 2nd, 3rd, 4th or 5th).
Here is the query I currently use:
Declare #nowString varchar(19)
Declare #nowDateString varchar(19)
Declare #now datetime
Declare #lastMinute datetime
Declare #nowDate datetime
Set #nowString = '#currentDateTime#:00'
Set #nowDateString = LEFT(#nowString, 10)
set #now = #nowString
set #nowDate = DATEADD(dd, 0, DATEDIFF(dd, 0, #now))
set #lastMinute = DATEADD(mi, -1, #now)
select *
from message_prepared
where schedule = '1'
and active = '1'
and noaa = '0'
and (
(
schedule_type = 'recurring'
and startdate <= #nowDate
and isnull(enddate, DATEADD(yy, 1, #nowDate)) >= #nowDate
and (
#nowDateString + ' ' + isnull(recurring_start_time_hour, '00') + ':' + isnull(recurring_start_time_min, '00') + ':00' = #now
or #nowDateString + ' ' + isnull(recurring_start_time_hour, '00') + ':' + isnull(recurring_start_time_min, '00') + ':00' = #lastMinute
)
-- Test for different type of recurring
and (
( ltrim(rtrim(recurring)) = 'M' and DATEPART(dd, startdate) = DATEPART(dd, #now) )
or ( ltrim(rtrim(recurring)) = 'W' and DATEPART(dw, startdate) = DATEPART(dw, #now) )
or ltrim(rtrim(recurring)) = 'D'
)
)
or (
schedule_type = 'once'
and startdate = #nowDate
and (
#nowDateString + ' ' + onetime_start_time_hour + ':' + onetime_start_time_min + ':00' = #now
or #nowDateString + ' ' + onetime_start_time_hour + ':' + onetime_start_time_min + ':00' = #lastMinute
)
)
)
and repeat_multiple_times = 0
UNION ALL
SELECT *
FROM MESSAGE_PREPARED
WHERE schedule = '1'
AND active = 1
AND noaa = 0
AND recurring = 'D'
AND repeat_multiple_times = 1
AND startDate IS NOT NULL
AND recurring_start_time_hour IS NOT NULL
AND recurring_start_time_hour < 24
AND recurring_start_time_min IS NOT NULL
AND recurring_start_time_min < 60
AND startdate <= #nowDate
AND ISNULL(enddate, DATEADD(yy, 1, #nowDate)) >= #nowDate
AND
(
CASE WHEN repeat_unit = 'M'
THEN
DATEDIFF(n,
CONVERT(DATETIME,
CAST(DATEPART(yyyy, startDate) AS VARCHAR(4)) + '-' +
CAST(DATEPART(mm, startDate) AS VARCHAR(2)) + '-' +
CAST(DATEPART(dd, startDate) AS VARCHAR(2)) + ' ' +
CAST(recurring_start_time_hour AS VARCHAR(2)) + ':' +
CAST(recurring_start_time_min AS VARCHAR(2)) + ':00', 20),
GETDATE()) % repeat_interval
ELSE
DATEDIFF(n,
CONVERT(DATETIME,
CAST(DATEPART(yyyy, startDate) AS VARCHAR(4)) + '-' +
CAST(DATEPART(mm, startDate) AS VARCHAR(2)) + '-' +
CAST(DATEPART(dd, startDate) AS VARCHAR(2)) + ' ' +
CAST(recurring_start_time_hour AS VARCHAR(2)) + ':' +
CAST(recurring_start_time_min AS VARCHAR(2)) + ':00', 20),
GETDATE()) % (repeat_interval * 60)
END = 0
OR
CASE WHEN repeat_unit = 'M'
THEN
(DATEDIFF(n,
CONVERT(DATETIME,
CAST(DATEPART(yyyy, startDate) AS VARCHAR(4)) + '-' +
CAST(DATEPART(mm, startDate) AS VARCHAR(2)) + '-' +
CAST(DATEPART(dd, startDate) AS VARCHAR(2)) + ' ' +
CAST(recurring_start_time_hour AS VARCHAR(2)) + ':' +
CAST(recurring_start_time_min AS VARCHAR(2)) + ':00', 20),
GETDATE()) - 1) % repeat_interval
ELSE
(DATEDIFF(n,
CONVERT(DATETIME,
CAST(DATEPART(yyyy, startDate) AS VARCHAR(4)) + '-' +
CAST(DATEPART(mm, startDate) AS VARCHAR(2)) + '-' +
CAST(DATEPART(dd, startDate) AS VARCHAR(2)) + ' ' +
CAST(recurring_start_time_hour AS VARCHAR(2)) + ':' +
CAST(recurring_start_time_min AS VARCHAR(2)) + ':00', 20),
GETDATE()) - 1) % (repeat_interval * 60)
END = 0
)
This will only occur when reocurring is set to "M" and I would like to determine if today is the specific day of the week, week of the month and hour/min.

Answer 1

This is pretty simple logic. Today is the nth DOW of the month when the following is true:
Today is that day of the week
The day of the month is between 7*(n-1) + 1 and 7 * n
So, the first Monday of the month is always between the 1st and 7th, and so on. Here is an example case statement to test this:
declare #DayOfWeek varchar(255) = 'Thursday';
declare #Which int = 3;
select (case when datename(dw, Today) = #DayOfWeek and
(DAY(Today) - 1) / 7 = #Which - 1
then 1
else 0
end)
from (select CAST(getdate() as date) as Today) t
I've structured the query this way so you can test it with different values. Just replace the expression that defines Today, with something like getdate() - 3 or '2013-01-01'.