Question

Can anyone help me with this please.
I want to do something like this.

strSQL = SELECT  [filename1].[" & xlSheet.Name & "$].Col1
, [filename1].[" & xlSheet.Name & "$].Col2
FROM [filename1].[" & xlSheet.Name & "$]
UNION ALL
SELECT [filename2].[" & xlSheet2.Name & "$].Col1
, [filename2].[" & xlSheet2.Name & "$].Col2
FROM  [Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filename2+ ";Extended Properties=Excel 12.0;HDR=Yes].[" & xlSheet2.Name & "$]
WHERE [filename1].[" & xlSheet.Name & "$].Col1= [filename2].[" & xlSheet2.Name & "$].Col1

Using conExcel As New OleDb.OleDbConnection()
conExcel.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filename1 + ";Extended Properties=Excel 12.0;HDR=Yes"
conExcel.Open()
cmdSelect.CommandText = strSQL
cmdSelect.Connection = conExcel
intRowsCount = cmdSelect.ExecuteNonQuery()

Answer 1

You cannot address two different files with the one OleDb connection. You’ll need to create another connection for the second file and pull the data in that way.

Here’s how I usually code a method to retrieve all data from a sheet:

private DataTable RetrieveData(string filename, string sheetName)
{
    string connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filename + ";Extended Properties=\"Excel 12.0;HDR=YES\"";
    string query = "SELECT * from [" + sheetName + "$]";
    DataTable dt = new DataTable();

    using (OleDbConnection conn = new OleDbConnection(connectionString))
    {
        conn.Open();

        using (OleDbDataAdapter dataAdapter = new OleDbDataAdapter(query, conn))
        {
            dataAdapter.Fill(dt);
        }

        conn.Close();
    }

    return dt;
}

And then you can just call it with each of your files:

DataTable dt1 = RetrieveData("filename1.xlsx", "Sheet1");
DataTable dt2 = RetrieveData("filename2.xlsx", "Sheet1");