SQL for fetching all date/times on a single date - sql

Question

I have a table of whose rows contain a date/time filled with appointment times. The appointment times are a single field (i.e. the date and the time together). I've created a recordset to fetch all the appointments which occur on a given date:
Dim dt as date
dt = #3/2/2019#
Set rs = Currentdb.OpenRecordSet("SELECT stuff FROM Appt WHERE
Int(Appt.apptTime) = #" & dt & "#") --------
This works, but the "Int" function makes it inefficient. One solution would be to separate the date/time field into two fields (date and time) then just search on the date field. Unfortunately, I don't have the option of modifying the database structure.
Does anyone have a suggestion of how I can make this fetch more efficient?

Answer 1

You must format the date expressions properly and remember the equal option:
Set rs = Currentdb.OpenRecordSet("SELECT stuff FROM Appt WHERE Appt.apptTime >= #" & Format(dt, "yyyy\/mm\/dd") & "# AND Appt.apptTime < #" & Format(DateAdd("d", 1, dt), "yyyy\/mm\/dd") & "#")

Answer 2

I just figured out a solution:
WHERE (Appt.apptTime > #" & dt & "#) AND (Appt.apptTime < #" & dt + 1 & "#")

Answer 3

You can use DateValue(Appt.apptTime)
eg:
"WHERE ( DateVaue(Appt.apptTime) = #" & dt & "#"
The above will return only the date part and remove the time portion.
However, the above can't use high-speed indexing. So, your follow answer of :
WHERE (Appt.apptTime > #" & dt & "#) AND (Appt.apptTime < #" & dt + 1 & "#")
will run much faster. The only other issue is that you should (need) to force the format to USA format, else your posted solution can fail depending on the users reginal (date format) settings. So, on some computer you find the above will not work, or fail, or even get things like 4/5/2020 mixed up. Is that April 5, or May 4th?
So, you need to correctly format the date to USA and ensure that you IGNORE the users date format, else your code will fail on many computers with different date formats.
You should create a helper function for this, like this:
Public Function quDateT(dt As Date) As String
' return formatted date
quDateT = "#" & Format(dt, "mm\/dd\/yyyy HH:NN:SS") & "#"
End Function
Then, your query becomes:
WHERE (Appt.apptTime > " & qudateT(dt) & ") AND (attt.apptTime < " & qudateT(dt + 1)
Now in your case, DT will not have time, so the time portion of qudateT will be 00:00:00.
So, your example follow up should work, but you want to FORCE the date format to MM/DD/YYYY (USA) format, and if users have their setting such as DD/MM/YYYY, then your example query will fail on computers with such (different) regional settings.

Answer 4

I don't see why date formatting matter as all dates, regardless of displayed format, are stored as double-precision, floating-point numbers. The integer portion being the number of days since December 30, 1899; the fractional portion being the fraction of the 24-hour day. So my computation (in my updated "found a solution" post), which treats the dates as numbers should be immune to whatever date format has been chosen for the display of dates, right?