"Too many fields defined" when querying Excel using ADO - sql

Question

I'm querying an Excel 2010 workbook using the following ADO:
Function WorksheetRecordsetSQL(workbookPath As String, sheetName As String, selectSQL As String) As ADODB.Recordset
Dim objconnection As New ADODB.Connection
Dim objrecordset As New ADODB.Recordset
Const adOpenStatic = 3
Const adLockOptimistic = 3
Const adCmdText = &H1
objconnection.CommandTimeout = 99999999
objconnection.Open "Provider=Microsoft.ACE.OLEDB.12.0;" & _
"Data Source=" & workbookPath & ";" & _
"Extended Properties=""Excel 12.0 Xml;HDR=YES;IMEX=1"";"
objrecordset.Open selectSQL, _
objconnection, adOpenStatic, adLockOptimistic, adCmdText
Set WorksheetRecordsetSQL = objrecordset
End Function
When I call it with this SQL:
Select * FROM [someWorksheet$]
the function executes successfully. But if I call it with:
Select *,cdate(someField) FROM [someWorksheet$]
then I get this error:
Too many fields defined.
I found that the select * query was producing a recordset with 255 fields (the maximum that the Access engine can have in a query), even though there are only 58 columns in the sheet. So that one extra cdate() column overloaded the engine and produced the error.
Is there a way that I can keep a select * query from picking up blank columns from an Excel sheet? Or some parameters that I can set that will allow more than 255 fields?

Answer 1

You can specify the range which should be read and so reduce the number of columns entering into the query. Here from cell A1 to column BF (58) all rows:
FROM [Source_sheet$A1:BF]
Sub main()
Dim reultingRecordset As ADODB.Recordset
Set reultingRecordset = WorksheetRecordsetSQL( _
"C:\Temp\VBA\ReadWithADOSource.xlsx", _
"Source_sheet", _
"Select * FROM [Source_sheet$]")
Debug.Print "Select * FROM [Source_sheet$] >"
Debug.Print "Fields: " & reultingRecordset.Fields.Count & " Records: " & reultingRecordset.RecordCount
Set reultingRecordset = WorksheetRecordsetSQL( _
"C:\Temp\VBA\ReadWithADOSource.xlsx", _
"Source_sheet", _
"Select *,cdate(Col2) FROM [Source_sheet$A1:BF]")
Debug.Print "Select *,cdate(Col2) FROM [Source_sheet$A1:BC] > "
Debug.Print "Fields: " & reultingRecordset.Fields.Count & " Records: " & reultingRecordset.RecordCount
End Sub
Output:
Select * FROM [Source_sheet$] >
Fields: 255 Records: 8
Select *,cdate(Col2) FROM [Source_sheet$A1:BC] >
Fields: 59 Records: 8