Answered Using Join Alias

{
  "formtabs":[
    {
      "MIGX_id":10,
      "caption":"Category",
      "print_before_tabs":"0",
      "fields":[
        {
          "MIGX_id":19,
          "field":"category",
          "caption":"Category",
          "description":"",
          "description_is_code":"0",
          "inputTV":"",
          "inputTVtype":"",
          "validation":"",
          "configs":"",
          "restrictive_condition":"",
          "display":"",
          "sourceFrom":"config",
          "sources":"",
          "inputOptionValues":"",
          "default":"",
          "useDefaultIfEmpty":"0",
          "pos":1
        }
      ],
      "pos":1
    }
  ],
  "contextmenus":"update||duplicate||remove",
  "actionbuttons":"addItem",
  "columnbuttons":"update||remove",
  "filters":"",
  "extended":{
    "migx_add":"",
    "disable_add_item":"",
    "add_items_directly":"",
    "formcaption":"",
    "update_win_title":"",
    "win_id":"",
    "maxRecords":"",
    "addNewItemAt":"bottom",
    "multiple_formtabs":"",
    "multiple_formtabs_label":"",
    "multiple_formtabs_field":"",
    "multiple_formtabs_optionstext":"",
    "multiple_formtabs_optionsvalue":"",
    "actionbuttonsperrow":4,
    "winbuttonslist":"",
    "extrahandlers":"this.handleColumnSwitch",
    "filtersperrow":4,
    "packageName":"staff",
    "classname":"StaffCategory",
    "task":"staff_categories",
    "getlistsort":"",
    "getlistsortdir":"",
    "sortconfig":"",
    "gridpagesize":"",
    "use_custom_prefix":"0",
    "prefix":"",
    "grid":"",
    "gridload_mode":2,
    "check_resid":"0",
    "check_resid_TV":"",
    "join_alias":"",
    "has_jointable":"yes",
    "getlistwhere":"",
    "joins":"",
    "hooksnippets":"",
    "cmpmaincaption":"",
    "cmptabcaption":"",
    "cmptabdescription":"",
    "cmptabcontroller":"",
    "winbuttons":"",
    "onsubmitsuccess":"",
    "submitparams":""
  },
  "columns":[
    {
      "MIGX_id":1,
      "header":"ID",
      "dataIndex":"id",
      "width":"",
      "sortable":"false",
      "show_in_grid":1,
      "renderer":"",
      "clickaction":"",
      "selectorconfig":"",
      "renderchunktpl":"",
      "renderoptions":"",
      "editor":""
    },
    {
      "MIGX_id":2,
      "header":"Category",
      "dataIndex":"category",
      "width":"",
      "sortable":"false",
      "show_in_grid":1,
      "renderer":"",
      "clickaction":"",
      "selectorconfig":"",
      "renderchunktpl":"",
      "renderoptions":"",
      "editor":""
    },
    {
      "MIGX_id":3,
      "header":"Joined",
      "dataIndex":"joined",
      "width":"",
      "sortable":"false",
      "show_in_grid":1,
      "renderer":"this.renderSwitchStatusOptions",
      "clickaction":"switchOption",
      "selectorconfig":"",
      "renderchunktpl":"",
      "renderoptions":[
        {
          "MIGX_id":1,
          "name":"joined",
          "use_as_fallback":"",
          "value":1,
          "clickaction":"",
          "handler":"",
          "image":"assets\/components\/migx\/style\/images\/cb_ticked.png"
        },
        {
          "MIGX_id":2,
          "name":"unjoined",
          "use_as_fallback":1,
          "value":"0",
          "clickaction":"",
          "handler":"",
          "image":"assets\/components\/migx\/style\/images\/cb_empty.png"
        }
      ],
      "editor":""
    }
  ]
}

return $modx->error->success();