Return Results or False if none

/*
  $Results = MyFunctionName();
  if ($Results !== False)
  {
    foreach ($Results as $Result)
    {
      = $Result['MyColumnName'];
    }
  }
*/

  $sql = $wpdb->prepare("SELECT * FROM {$wpdb->prefix}my_table_name WHERE FileName = %s", $FileName);
  if (current_user_can('administrator'))
    $wpdb->show_errors();
  $Results = $wpdb->get_results($sql, ARRAY_A);
  if (count($Results) == 0)
    return(False);
  else
    return($Results);

Loop through all row results

  $sql = $wpdb->prepare("SELECT * FROM {$wpdb->prefix}my_table_name WHERE FileName = %s", $FileName);
  if (current_user_can('administrator'))
    $wpdb->show_errors();
  $Results = $wpdb->get_results($sql, ARRAY_A);
  foreach ($Results as $Result)
  {
    $MyValue = $Result['MyColumnName'];
  }

Get single result

  $sql = $wpdb->prepare("SELECT * FROM {$wpdb->prefix}my_table_name WHERE FileName = %s", $FileName);
  if (current_user_can('administrator'))
    $wpdb->show_errors();
  $Results = $wpdb->get_results($sql, ARRAY_A);
  if (count($Results) > 0)
  {
    $Result = $Results[0];       //Get the first row of the results
    $MyValue = $Result['MyColumnName'];
  }

Is a result returned?

 if (!isset($Result['MyColumnName']))
    return;

Select From Row + Value Array

/*
  $FieldNamesArray = array('ColumnName1', 'ColumnName2');
  $Results = db_user_read_fields(bp_loggedin_user_id(), $FieldNamesArray);
  $ColumnName1 = ['ColumnName1'];
  $ColumnName2 = ['ColumnName2'];
*/
function db_user_read_fields($user_id, $FieldNamesArray)
{
  global $wpdb;

  $sql = "SELECT ";

  $FirstField = true;
  foreach ($FieldNamesArray as $key)
  {
    if ($FirstField)
      $sql .= " $key ";
    else
      $sql .= ", $key ";
    $FirstField = false;
  }
  
  $sql .= $wpdb->prepare(" FROM {$wpdb->prefix}tbl_my_table WHERE user_id = %d", $user_id);

  $Results = $wpdb->get_results($sql, ARRAY_A);
  $Results = $Results[0];       //Get the first row of the results

  return ($Results);
}

Read SQL Server Time

//******************************************
//******************************************
//********** READ SQL SERVER TIME **********
//******************************************
//******************************************
function db_read_server_time ()
{
  global $wpdb;
  
  $sql ="SELECT NOW() as SqlServerDateTimeNow";
  if (current_user_can('administrator'))
    $wpdb->show_errors();
  $Results = $wpdb->get_results($sql, ARRAY_A);
  if (count($Results) > 0)
    return($Results[0]['SqlServerDateTimeNow']);
  else
    return("");     
}