I'm guessing the ParentTaskCd is used to link the tasks together.  Naturally adjust the code as needed to get the specific results you need, but this is a general way...

Assuming you don't have dates before 1980, then:

SELECT TOP (100) PERCENT DATEADD(MINUTE, ROUND(DATEDIFF(SECOND, base_date, DateTime) / 10.0, 0) * 30, base_date) AS Date_Time, SUM(Burner1) AS Burn1
FROM dbo.tblOilBurner
CROSS...

Here's a sample function using a physical tally table (it's not worth the trouble to me to try to use an inline tally table within a scalar function).  I've put...

Don't know if it's officially deprecated, but it has lots of issues, so, yeah, probably better to stick to decimal.

As to as_of_month, you'd be better off converting that to go...

1. bigint would be better.
2. date would be much better.
3. don't need to store.  Use code on the display side to show only year and month from the as_of_date column.

...

select * from table where sportyear=DATEADD(YEAR, -1, @year)

Please be more specific on "Does not work" for Q.ArrangementType.  In general you should have no problem referencing columns in the view in a NOT EXISTS, so some other error...

If you're truly on SQL 2016+, as you said, you can use SESSION_CONTEXT, as below.

It's easier if the tables have the exact same structure, but we could "fudge" around it...

Oops, yep, sorry.  A copy/paste where I accidentally left the ", 0" at the end.

Something along these lines:

Declare @jan01 date
Set @jan01 = Dateadd(Year, Datediff(Year, 0, GETDATE()), 0)

select
Case Left(PeriodID, 3)

When 'Jan' THEN Dateadd(Day, -1, Dateadd(Month, 1, @jan01), 0)

When 'Feb' THEN Dateadd(Day, -1,...

Use just one date for each month; in keeping with "standard" practice, I use the first of the month.

Also, you must remove H.Quantity from the GROUP BY.

select...

Again, MS is following the relational model, where a set does not have a defined order.  That may be fine theoretically, but in the real world we often do need...

Here's another alternative to splitting, to show how CROSS/OUTER APPLY can assign alias names to computed values that can be used in subsequent APPLYs and in the SELECT itself, without...

Presumably MS is following relational theory, where the order of a set doesn't matter.

But, in the real world, the order often does matter a lot, especially when the set has...

Note that you don't have to drop the index and re-create it.

Instead you can DISABLE it, then REBUILD it.

ALTER INDEX no_dups_index ON dbo.your_table DISABLE;

UPDATE your_table

SET ... = ... + 5

/*WHERE...