Demonstrates a custom template for showing a Participant Database list in "reverse" form: rows as fields and columns as records.

pdb-list-record-columns.php

<?php
/**
 * @version 1.1
 * 
 * PDbList template demonstrating how to show a "reverse" table with records as 
 * columns and fields as rows
 *
 */
/** @var PDb_List $this */

// sets up our variables
$header_column = 'full_name'; // name of the field to use as the header title for each record
$table_rows = array(); // holds the row data 
$header_row = array(''); // holds the header row as $title

/* this section fills the variables with the values from the list object 
 * in such a way as to be displayable in "reverse" format
 */
foreach ( $this->records as $record_id => $record_fields )
{
  foreach ( $record_fields as $field )
  {
    /** @var PDb_Field_Item $field */
    
    // if the current field is the header column field, put its value in the header row
    if ( $field->name() === $header_column )
    {
      $header_row[] = PDb_FormElement::get_field_value_display( $field );
      continue; // move on to the lext field
    }

    // if we're starting a new field row, store the field's title as the row header
    if ( !isset( $table_rows[$field->name()] ) )
    {
      $table_rows[$field->name()] = array($field->title());
    }

    $table_rows[$field->name()][] = PDb_FormElement::get_field_value_display( $field );
  }
}
?>

<div class="wrap <?php echo $this->wrap_class ?>" id="<?php echo $this->list_anchor ?>">

  <?php
  /** @see PDb_List::show_search_sort_form */
  $this->show_search_sort_form();
  ?>
  
  <table class="wp-list-table widefat fixed pages list-container" >

    <?php if ( has_action( 'pdb-prepend_to_list_container_content' ) ) : ?>
      <caption>
        <?php do_action( 'pdb-prepend_to_list_container_content' ) ?>
        <?php $this->print_list_count( '<div class="%s"><span class="list-display-count">' ) ?>
      </caption>
    <?php else : ?>
      <?php
      /* print the count if enabled in the shortcode
       * 
       * the tag wrapping the count statment can be supplied in the function argument, example here
       */
      $this->print_list_count( '<caption class="%s" ><span class="list-display-count">' );
      ?>
    <?php endif ?>


    <?php if ( $record_count > 0 ) : // print only if there are records to show  ?>
    
      <?php if ( count( $header_row ) > 1 ) : ?>
      <thead>
        <tr>
          <?php
          foreach ( $header_row as $header )
          {
            echo '<th>' . $header . '</th>';
          }
          ?>
        </tr>
      </thead>
      <?php endif ?>
      
      <tbody>

        <?php
        foreach ( $table_rows as $row )
        {
          echo '<tr>';
          foreach ( $row as $i => $field_value )
          {
            if ( $i === 0 )
            {
              echo '<th>' . $field_value . '</th>';
            } else
            {
              echo '<td>' . $field_value . '</td>';
            }
          }
          echo '</tr>';
        }
        ?>

      </tbody>

<?php else : // if there are no records     ?>

      <tbody>
        <tr>
          <td><?php if ( $this->is_search_result ) echo Participants_Db::plugin_setting( 'no_records_message' ) ?></td>
        </tr>
      </tbody>

  <?php endif; // $record_count > 0    ?>

  </table>
  <?php
  /*
   * this shortcut function presents a pagination control with default layout
   */
  $this->show_pagination_control();
  ?>
</div>

You will probably want to modify the value of $header_column to match the name of the field you want to use as the header for each column.

The HTML this generates is bare bones, you may want to add classes, etc.

Read the linked page if you don't know how to use Participants Database Custom Templates.