How to structure SQL Statement - sql-server

Question

I have a table that contains a list of tasks;
TableName: Tasks. Fields: (ID Int, Description nvarchar)
The tasks are completed daily and are logged in a table like follows;
TableName TasksDone. Fields: (TaskID Int, TaskDate DateTime)
I need to have a query that runs for a date range and shows the tasks that were NOT done (do not exist in the TasksDone table) for every date in the range.
I hope that makes sense...
Thanks for any help.

Answer 1

You will need a numbers or calendar table to make things easy, or we can simulate one if the range is small. Is the TaskDate a plain date, or does it have a time component also?
Basic plan of attack is:
declare #StartDate datetime
declare #EndDate datetime
/* Set #StartDate and #EndDate to represent the range */
with Digits as (
select 0 as d union all select 1 union all select 2 union all select 3 union all select 4 union all
select 5 union all select 6 union all select 7 union all select 8 union all select 9
), Numbers as (
select (D1.d * 100) + (D2.d * 10) + D3.d as n
from Digits D1,Digits D2,Digits D3
), TaskDates as (
select
t.TaskID,
DATEADD(day,n.n,#StartDate) as TaskDate
from
Tasks t
inner join
Numbers n
on
DATEADD(day,n.n,#StartDate) <= #EndDate
)
select
*
from
TaskDates td1
left join
TasksDone td2
on
td1.TaskID = td2.TaskID and
DATEDIFF(day,td1.TaskDate,td2.TaskDate) = 0
where
td2.TaskID is null
The first two CTEs build a small numbers table, the 3rd CTE constructs a set of TaskIDs and Dates within the required range. The final select matches theses against the TasksDone table, and then discards those rows where a match is found. If TasksDone.TaskDate is a plain date (no time component) and #StartDate is also with no time component, then you can ditch the DATEDIFF and just use td1.TaskDate = td2.TaskDate.
If you need a large range (above can cover ~3 years), I'd suggest building a proper number table or calendar table

Answer 2

This is fairly straight forward, if I'm understanding the problem correctly:
SELECT *
FROM Tasks
WHERE ID NOT IN (SELECT TaskID FROM TasksDone WHERE TaskDate BETWEEN x AND y)
Replace x and y with the date you're after.

Answer 3

I've not tested this out but see if this helps:
select ID, TaskDate as A from Tasks,TasksDone
where TaskID not in (select TaskID from TasksDone where TaskDate = A)
GROUP BY TaskDate

Answer 4

If I understand correct, following statement should get you the tasks that didn't get executed every day in the entire range.
SQL Statement
SELECT t.*
FROM #Tasks t
INNER JOIN (
SELECT TaskID
FROM #TasksDone td
WHERE td.TaskDate BETWEEN #RangeStart AND #RangeEnd
GROUP BY
td.TaskID
HAVING COUNT(TaskID) < CAST(#RangeEnd - #RangeStart AS INTEGER)+1
UNION ALL
SELECT TaskID
FROM #TasksDone td
WHERE TaskID NOT IN (SELECT TaskID
FROM #TasksDone
WHERE TaskDate BETWEEN #RangeStart AND #RangeEnd)
) td ON td.TaskID = t.ID
Test script
DECLARE #Tasks TABLE (
ID INTEGER
, DESCRIPTION NVARCHAR(32)
)
DECLARE #TasksDone TABLE (
TaskID INTEGER
, TaskDate DATETIME
)
DECLARE #RangeStart DATETIME
DECLARE #RangeEnd DATETIME
SET #RangeStart = GetDate() - 1
SET #RangeEnd = GetDate() + 1
INSERT INTO #Tasks
SELECT 1, 'Done Every Day in range.'
UNION ALL SELECT 2, 'Done a few times in range.'
UNION ALL SELECT 3 , 'Not done anytime in range.'
INSERT INTO #TasksDone
SELECT 1, #RangeStart
UNION ALL SELECT 1, GetDate()
UNION ALL SELECT 1, #RangeEnd
UNION ALL SELECT 2, GetDate()
UNION ALL SELECT 3, GetDate() + 2
SELECT t.*
FROM #Tasks t
INNER JOIN (
SELECT TaskID
FROM #TasksDone td
WHERE td.TaskDate BETWEEN #RangeStart AND #RangeEnd
GROUP BY
td.TaskID
HAVING COUNT(TaskID) < CAST(#RangeEnd - #RangeStart AS INTEGER)+1
UNION ALL
SELECT TaskID
FROM #TasksDone td
WHERE TaskID NOT IN (SELECT TaskID FROM #TasksDone WHERE TaskDate BETWEEN #RangeStart AND #RangeEnd)
) td ON td.TaskID = t.ID