I have this little method that i use to get stuff from SQL. I either call it with varSearch = "" or varSearch = "something". I would like to know if having method written this way is best or would it be better to split it into two methods (by overloading), or maybe i could somehow parametrize whole WHERE clausule?

private void sqlPobierzKontrahentDaneKlienta(ListView varListView, string varSearch) {
        varListView.BeginUpdate();
        varListView.Items.Clear();
        string preparedCommand;
        if (varSearch == "") {
            preparedCommand = @"
                SELECT t1.[KlienciID],
                CASE WHEN t2.[PodmiotRodzaj] = 'Firma' THEN
                          t2.[PodmiotFirmaNazwa] ELSE 
                          t2.[PodmiotOsobaNazwisko] + ' ' + t2.[PodmiotOsobaImie] END AS 'Nazwa'
                FROM [BazaZarzadzanie].[dbo].[Klienci] t1
                INNER JOIN [BazaZarzadzanie].[dbo].[Podmioty] t2
                ON t1.[PodmiotID] = t2.[PodmiotID]
                ORDER BY t1.[KlienciID]";
        } else {
            preparedCommand = @"
                SELECT t1.[KlienciID],
                CASE WHEN t2.[PodmiotRodzaj] = 'Firma' THEN
                          t2.[PodmiotFirmaNazwa] ELSE 
                          t2.[PodmiotOsobaNazwisko] + ' ' + t2.[PodmiotOsobaImie] END AS 'Nazwa'
                FROM [BazaZarzadzanie].[dbo].[Klienci] t1
                INNER JOIN [BazaZarzadzanie].[dbo].[Podmioty] t2
                ON t1.[PodmiotID] = t2.[PodmiotID]
                WHERE t2.[PodmiotOsobaNazwisko] LIKE @searchValue OR t2.[PodmiotFirmaNazwa] LIKE @searchValue OR t2.[PodmiotOsobaImie] LIKE @searchValue
                ORDER BY t1.[KlienciID]";
        }
        using (var varConnection = Locale.sqlConnectOneTime(Locale.sqlDataConnectionDetails))
        using (SqlCommand sqlQuery = new SqlCommand(preparedCommand, varConnection)) {
            sqlQuery.Parameters.AddWithValue("@searchValue", "%" + varSearch + "%");
            using (SqlDataReader sqlQueryResult = sqlQuery.ExecuteReader())
                if (sqlQueryResult != null) {
                    while (sqlQueryResult.Read()) {
                        string varKontrahenciID = sqlQueryResult["KlienciID"].ToString();
                        string varKontrahent = sqlQueryResult["Nazwa"].ToString();
                        ListViewItem item = new ListViewItem(varKontrahenciID, 0);
                        item.SubItems.Add(varKontrahent);
                        varListView.Items.AddRange(new[] {item});
                    }
                }
        }
        varListView.EndUpdate();
    }