Sumproduct in Excel VBA using function arguments as source - sql

Question

I'm trying to write a VBA function that takes the function arguments as the source and then runs SQL commands on it. The SQL command I'm currently trying to implement as a first step is the equivalent of Excel's sumproduct() function, which in SQL would be something along the lines of "SELECT SUM(A * B)".
I modified some code from another site that used SQL to convert an Excel table into a single column, and modified it to calculate a sumproduct, but I'm having trouble converting the subroutine into a function.
Current working code:
Sub doSQL()
Dim strCon As String
Dim oneSQL As String
' refer to 'microsoft activex data objects library'
Dim cn As Object
Dim rs As Object
Set cn = CreateObject("ADODB.Connection")
Set rs = CreateObject("ADODB.Recordset")
strCon = "Provider=Microsoft.ACE.OLEDB.12.0;" & _
"Data Source='" & ThisWorkbook.FullName & "';" & _
"Extended Properties='Excel 12.0;HDR=No;IMEX=1';" ' HDR=No means no headers (field names)
cn.Open strCon ' open connection
'-------------------------------------------------------------------------------
' F1, F2, F3 are the default fieldnames when no headers are included with data
oneSQL = "SELECT sum(F1 * F2) FROM [Sheet1$B:D] where F1 not like '' AND F2 not like ''"
rs.Open oneSQL, cn ' get recordset
Sheets("Sheet1").Range("A:A").ClearContents
Sheets("Sheet1").Range("A1").CopyFromRecordset rs ' copy recordset to worksheet
'-------------------------------------------------------------------------------
rs.Close
cn.Close
Set rs = Nothing
Set cn = Nothing
End Sub
The end result is that cell A1 returns the equivalent of sumproduct(B3:B5,C3:C5).
My attempt to convert it into a function:
Function SQL_sumproduct(A As Variant, B As Variant) As Double
Dim strCon As String
Dim oneSQL As String
' refer to 'microsoft activex data objects library'
Dim cn As Object
Dim rs As Object
Set cn = CreateObject("ADODB.Connection")
Set rs = CreateObject("ADODB.Recordset")
strCon = "Provider=Microsoft.ACE.OLEDB.12.0;" & _
"Data Source='" & ThisWorkbook.FullName & "';" & _
"Extended Properties='Excel 12.0;HDR=No;IMEX=1';" ' HDR=No means no headers (field names)
cn.Open strCon ' open connection
oneSQL = "SELECT sum(A * B)"
rs.Open oneSQL, cn ' get recordset
'-------------------------------------------------------------------------------
' Sheets("Sheet1").Range("A:A").ClearContents
' Sheets("Sheet1").Range("A3").CopyFromRecordset rs ' copy recordset to worksheet
'-------------------------------------------------------------------------------
SQL_sumproduct = rs
rs.Close
cn.Close
Set rs = Nothing
Set cn = Nothing
End Function
I end up getting an error because the code does not recognise the function arguments A and B as a source.
Could anyone give me some guidance as to how the "Data Source" parameter can be modified to recognise the function arguments?

Answer 1

The SQL statement in oneSQL = "SELECT sum(A * B)" is looking for fields named "A" and "B" (regardless of what is passed into the function in the parameters A and B). This is because A and B are enclosed in double-quotes.
To incorporate the parameters into the SQL statement, you would write this instead:
oneSQL = "SELECT sum(" & A & " * " & "B)"
Having A and B outside the double quotes causes them to be replaced with their values. & is the string concatenation operator which joins all of the pieces together.
Note: when dynamically constructing an SQL statement from any kind of external input, consider the possibility of SQL injection - see here and here