Export to excel faster

**Stewart Ross** · Aug 3 '08, 07:57 AM

Hi. The fastest way to export data to Excel will not work in your case, because you have so much cell formatting to do. Looking at your code I doubt there is much more you can do to it to speed it up unless you lose the formatting, as it is the formatting itself which is slowing things down.

The fastest way to transfer data to Excel is to use a variant array to store the data, an array whose dimensions are reset to match the current number of rows and columns you need to transfer. Instead of accessing Excel directly, loop processing transfers data to the array, and then as a final step the array is assigned to Excel in one operation. This is much faster (around 10 times as fast) than using the Cells method to write data to Excel cell-by-cell.

How I resolve it in cases such as yours is to open a pre-formatted Excel worksheet - a template sheet, although not an XLT file as such - and copy the data to the pre-formatted cells using the array method. I size the template to the maximum which the data will ever need, then delete any unused rows/columns within the processing of the worksheet after transferring the data from the array.

This hybrid method works well for me, and may be something you wish to consider at a later date.

-Stewart

Code extract from one transfer routine, with use of dynamic array picked out

Code:

Dim RowData() As Variant '<< DYNAMIC ARRAY
Dim RowRef As Long, ColRef As Long
Dim CellRange As Excel.Range
' ...
FirstPass = True
RowCounter = 0
Set RS = CurrentDb.OpenRecordset(ProgQueryName)
Do Until RS.EOF
	...
    If PrevDept <> DeptRef Then
	If Not FirstPass Then
	...
	End If
	FirstPass = False
	ReDim RowData(MaxProgs, MaxCols) << SET UP ACTUAL DIMENSIONS
	    ...
    End If
    RowData(RowCounter, 0) = CourseName ' << WRITE DATA TO THE ARRAY
    RowData(RowCounter, 1) = Block
    RowData(RowCounter, 2) = FEHE
    RowData(RowCounter, 4 + SessionOffset) = Enr
	...
    PrevDept = DeptRef
    RS.MoveNext
Loop
RS.Close
If Not FirstPass Then
    With xlRep.CurrentWorkSheet
	Set CellRange = .Range(.Cells(StartRow, 2), .Cells(StartRow + RowCounter - 1, MaxCols + 1)) '<< SET UP THE CELL RANGE FOR THE ARRAY TRANSFER
    End With
    CellRange.Value = RowData '<< TRANSFER DATA FROM ARRAY TO EXCEL
    xlRep.DeleteRows RowCounter + StartRow, LastRow
	...
End If

**svdoerga** · Aug 5 '08, 09:18 AM

Originally posted by Stewart Ross Inverness

Hi. The fastest way to export data to Excel will not work in your case, because you have so much cell formatting to do. Looking at your code I doubt there is much more you can do to it to speed it up unless you lose the formatting, as it is the formatting itself which is slowing things down.

The fastest way to transfer data to Excel is to use a variant array to store the data, an array whose dimensions are reset to match the current number of rows and columns you need to transfer. Instead of accessing Excel directly, loop processing transfers data to the array, and then as a final step the array is assigned to Excel in one operation. This is much faster (around 10 times as fast) than using the Cells method to write data to Excel cell-by-cell.

How I resolve it in cases such as yours is to open a pre-formatted Excel worksheet - a template sheet, although not an XLT file as such - and copy the data to the pre-formatted cells using the array method. I size the template to the maximum which the data will ever need, then delete any unused rows/columns within the processing of the worksheet after transferring the data from the array.

This hybrid method works well for me, and may be something you wish to consider at a later date.

-Stewart

Thanks a lot for your reply Stewart. Too bad I can't use your method in my case, since I would lose the formatting. It is good to know there is such a fast way to export data to excel though. I should be able to use it in the future, thanks!

**NeoPa** · Aug 5 '08, 08:00 PM

Would a Copy/Paste not do the trick pretty efficiently?

I'm planning that shortly in a current project.

**Stewart Ross** · Aug 5 '08, 10:31 PM

Hi NeoPa. Copy/Paste does work - but it is tabular in format (so no ability to define where the data goes if you need a particular cell layout that is not just rectangular), is actually slower than other methods (the copy to the clipboard has to be complete before the data can be pasted at all), and the default paste overwrites any formatting. Although Paste Text can be used to resolve the formatting problem, it in turn can cause problems with fields formatted in certain ways (numerics formatted with leading zeros for example).

In copying recordsets to Excel the Excel copy from recordset method is far faster than copy-paste. The use of a dynamic variant array is similarly fast, particularly for data that is not strictly tabular throughout.

What really slows Excel automation down is any form of range or worksheet selection prior to copying a value, and using bespoke formatting a cell at a time. To take an instance, to form a border round a single cell means making at least four automation calls between Access and Excel with all the communication overheads that are entailed along with it. Range formatting is more efficient, because the range can be formatted in more or less the same number of communication calls as a single cell.

-Stewart

**NeoPa** · Aug 5 '08, 10:40 PM

Thanks for all that Stewart.

I always try to do my formatting by range where possible, and I have recently come across some of the problems associated with transferring data between cells in Excel. I tend to use the .Value = .Value approach where possible, but that tends to require formatting beforehand and afterwards.

I will see what I can come up with in my project - then I may get back to you for some further clarification on any outstanding matters. Obviously in another thread, as I don't want to hijack this one any further than I have already :D

Export to excel faster

Export to excel faster

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