Creating Excel file with info from database - excel

Question

I have a query that returns something like this:
1 2 3 4 5 6 7
A. B. C. D. E. F. G.
Etc...
Etc...
N rows
I store the query on a dataset. Then I create the Excel file using something like this:
Sql=“select * from table”
Dim cmd As New SqlDataAdapter(Sql, con)
Dim ds As New DataSet
cmd.Fill(ds)
For i=0 To Tables(0).Rows.Count - 1
For x=0 To ds.Tables(0).Columns.Count - 1
ExcelFile.Cells(i+1;x+1)=ds.Tables(0).Rows(i).Item(j)
Next
Next
The code works fine except that I need to write also columns headers name (1,2,3,4,etc.) My first que question is how can I add the headers?
And the main problem... the query sometimes is going to return more than 80k results, so following the for loop logic my code is going to run 80k times for every column (in this case 7 times) which is going to give me a slow result.
There is another fast way to fill and Excel file? Or this is the best way to do it?

Answer 1

You have access to the ColumnName property of each Column in your DataTable. For example, to just add the headers with as little modification of your code as possible, you could just do this:
'Write ColumnName to the corresponding cell in row 1
For x=0 To ds.Tables(0).Columns.Count - 1
ExcelFile.Cells(1, x+1) = ds.Tables(0).Columns(x).ColumnName
Next
'Modded to start at the second row and fix index variable
For i=1 To Tables(0).Rows.Count - 1
For x=0 To ds.Tables(0).Columns.Count - 1
ExcelFile.Cells(i+1, x+1) = ds.Tables(0).Rows(i).Item(x)
Next
Next
You are right to be concerned about the performance of this, though. The number one rule of Excel automation is to actually interact with Excel as little as possible, because each interaction is very expensive.
Assuming you are using regular Office Interop, you should build a 2-dimensional array representing the values from your query. You then find an equivalent size range in your worksheet, and set the value of that range to the array. This way you've cut many thousands of interactions to just one.
Dim rowCount = ds.Tables(0).Rows.Count
Dim colCount = ds.Tables(0).Columns.Count
Dim ws = ExcelFile
Dim valueSet(,) As Object
ReDim valueSet(rowCount - 1, colCount - 1)
For row = 0 To rowCount - 1
For col = 0 To colCount - 1
valueSet(row, col) = ds.Tables(0).Rows(row).Item(col)
Next
Next
'Set the entire set of values in a single operation
ws.Range(ws.Cells(1, 0), ws.Cells(rowCount, colCount).Value = valueSet
Also, if you actually are using Excel Interop or a wrapper around it like NetOffice, you should look into EPPlus and see if it does what you need. It's a helper library that works with OfficeOpenXML and doesn't even require Excel to be installed.

Answer 2

I use the following:
Dim sSql As String
Dim tbl As ListObject
'Declare a Connection object
Dim cnDB As New ADODB.Connection
'Declare a Recordset Object
Dim rs As ADODB.Recordset
' Housekeeping, set the connection strings
Set cnn = New ADODB.Connection
cnn.Provider = "MSDASQL"
cnn.CommandTimeout = 100
Set tbl = ActiveSheet.ListObjects("Lookup")
With tbl.DataBodyRange
If .Rows.Count > 1 Then
.Offset(1, 0).Resize(.Rows.Count - 1, .Columns.Count).Rows.Delete
End If
End With
' Connect to the database and paste new data
cnn.ConnectionString = "driver={};server={};uid={};pwd={};database={}"
sSql = "SELECT BLAH BLAH "
cnn.Open
Set rs = cnn.Execute(sSql)
ThisWorkbook.Worksheets("Lookup").Range("A2").CopyFromRecordset rs
cnn.Close