First, didn't know MySQL cost, thought it was "free" from Oracle.
Second, you are asking for a lot of a forum where almost everyone works for free (our time).
So,...

There may be a better way that is more performant and scalable, but I don't have the time at the moment as I am also working.

Here is my code:

SELECT
[m].*
FROM
mytable AS [m]
WHERE
[m].[dt_close_time] >= DATEADD(HOUR,23,DATEADD(DAY,DATEDIFF(DAY,0,[m].[dt_close_time]),0)) AND
[m].[dt_close_time] < DATEADD(HOUR,31,DATEADD(DAY,DATEDIFF(DAY,0,[m].[dt_close_time]),0))
ORDER...

Looks like a Son of Silver Spoon has disappeared because he didn't get the answers to both questions.  Not getting any response today.

Really need to see the code.  Without it, we are shooting in the dark.

Goes from 7-0 to 4-3, nothing in between.

So, what have you accomplished?

Except #tmp is unique if you were to look in tempdb.  The local #tmp table is uniquely named in tempdb.  This has to be true for local temporary tables or...