How can I combine these two SQL queries (Access/VBA) - sql

Question

I am using two SQL queries in VBA that i believe they could be done in one, but I cant get it to work. I Want to turn the VBA portion into a Query outside of VBA, the VBA keeps breaking my file due to the amount of data it processes. (By break i mean it gives a message that says "this file is not a valid database" rendering the file corrupted). I search for that error but all i found was not related to breaking because of VBA code.
Anyways, here are the two queries ran with VBA.
SELECT ET.VerintEID AS EID, Sum(ET.ExceptMin)/60 AS Exeptions
FROM Tbl_VExceptTime AS ET
INNER JOIN Tbl_VCodes ON ET.Exception = Tbl_VCodes.Exception
WHERE (ET.ExceptDate Between #" & sDate & "# And #" & eDate & "#)
GROUP BY ET.VerintEID, Tbl_VCodes.IsApd
HAVING Tbl_VCodes.IsApd = ""OFF"";
I loop these results to update a table.
Do While Not .EOF
SQL = "UPDATE Tbl_AttendanceByAgent SET EXC = " & recSet.Fields(1).Value & _
" WHERE VerintID = '" & recSet.Fields(0).Value & "'"
CurrentDb.Execute SQL
.MoveNext
Loop
I know that i can save the results from the first query into a table and without looping I can update the main table with another SQL query, but I believe it can be done on a single SQL. I have tried using an UPDATE with a SELECT of the first query but it just errors out on me with an invalid syntax.

Answer 1

Yes this could be achieved in one single query as shown below
UPDATE Tbl_AttendanceByAgent
SET Tbl_AttendanceByAgent.EXC = t2.Exeptions
from Tbl_AttendanceByAgent t1
inner join (
SELECT ET.VerintEID AS EID, Sum(ET.ExceptMin)/60 AS Exeptions
FROM Tbl_VExceptTime AS ET
INNER JOIN Tbl_VCodes as TV ON ET.Exception = TV.Exception
WHERE (ET.ExceptDate Between #" & sDate & "# And #" & eDate & "#)
GROUP BY ET.VerintEID, TV.IsApd
HAVING Tbl_VCodes.IsApd = 'OFF'
) AS t2 on t2.EID = t1.VerintID
Note: I suppose you will replace sDate, eDate with values within your code

Answer 2

This question is an answer to the described errors and the given code, although it technically does not answer the request for a single SQL statement. I started adding a comment, but that's just too tedious when this answer box allows everything to be expressed efficiently at once.
First of all, referring to CurrentDb is actually NOT a basic reference to a single object instance. Rather it is more like a function call that generates a new, unique "clone" of the underlying database object. Calling it over and over again is known to produce memory leaks, and at the least is very inefficient. See MS docs for details.
Although the given code is short, it's not sweet. Not only is it repeatedly creating new database objects, it is repeatedly executing an SQL statement to update what I assume is a single row each time. That also entails regenerating the SQL string each time.
Even if executing the SQL statement repeatedly was an efficient option, there are better ways to do that, like creating a temporary (in-memory) QueryDef object with parameters. Each loop iteration then just resets the parameters and executes the same prepared SQL statement.
But in this case, it may actually be more efficient to load the table being updated into a DAO.Recordset, then use the in-memory Recordset to search for a match, then use the recordset to update the row.
I suspect that addressing a couple of those issues would make your VBA code viable.
Dim db as Database
Set db = CurrentDb 'Get just a single instance and reuse
Dim qry as QueryDef
SQL = "PARAMETERS pEXC Text ( 255 ), pID Long; " & _
" UPDATE Tbl_AttendanceByAgent SET EXC = pEXC " & _
" WHERE VerintID = pID"
set qry = db.CreateQueryDef("", SQL)
'With recSet '???
Do While Not .EOF
qry.Parameters("pEXC") = recSet.Fields(1).Value
qry.Parameters("pID") = recSet.Fields(0).Value
qry.Execute
.MoveNext
Loop
'End With recSet '???
'OR an alternative
Dim recUpdate As DAO.Recordset2
Set recUpdate = db.OpenRecordset("Tbl_AttendanceByAgent", DB_OPEN_TABLE)
Do While Not .EOF
recUpdate.FindFirst "VerintID = " & recSet.Fields(0).Value
If Not recUpdate.NoMatch Then
recUpdate.Edit
recUpdate.Fields("EXC") = recSet.Fields(1).Value
recUpdate.Update
End If
.MoveNext
Loop
I realized in commenting on Gro's answer, that the original query's aggregate clauses will produce unique values on EID, but it then becomes obvious that there is no need to group on (and sum) values which do not have Tbl_VCodes.IsApd = 'OFF'. The query would be more efficient like
SELECT ET.VerintEID AS EID, Sum(ET.ExceptMin)/60 AS Exeptions
FROM Tbl_VExceptTime AS ET
INNER JOIN Tbl_VCodes ON ET.Exception = Tbl_VCodes.Exception
WHERE (ET.ExceptDate Between #" & sDate & "# And #" & eDate & "#)
AND Tbl_VCodes.IsApd = 'OFF'
GROUP BY ET.VerintEID;
BTW, you could consider implementing the same temporary QueryDef pattern as I showed above, then you'd change the first WHERE expression to something like
PARAMETERS PsDate DateTime, PeDate DateTime;
...
WHERE (ET.ExceptDate Between [PsDate] And [PeDate])
...