Examples

Group relation to a single page

      'group_db_10' => [ 
         'exclude' => 1,
         'label' => 'group_db_10 allowed=pages size=1',
         'config' => [ 
            'type' => 'group',
            'internal_type' => 'db',
            'allowed' => 'pages',
            'maxitems' => 1,
            'minitems' => 0,
            'size' => 1,
            'default' => 0,
            'suggestOptions' => [ 
               'default' => [ 
                  'additionalSearchFields' => 'nav_title, alias, url',
                  'addWhere' => 'AND pages.doktype = 1',
               ],
            ],
         ],
      ],
      // Example from extension "styleguide", table "tx_styleguide_elements_group"

Group relation to be_groups and be_users

      'group_db_1' => [ 
         'exclude' => 1,
         'label' => 'group_db_1 allowed=be_users,be_groups description',
         'description' => 'field description',
         'config' => [ 
            'type' => 'group',
            'internal_type' => 'db',
            'allowed' => 'be_users,be_groups',
            'fieldControl' => [ 
               'editPopup' => [ 
                  'disabled' => false,
               ],
               'addRecord' => [ 
                  'disabled' => false,
               ],
               'listModule' => [ 
                  'disabled' => false,
               ],
            ],
         ],
      ],
      // Example from extension "styleguide", table "tx_styleguide_elements_group"