How do I add button on each row in datatable?

Basically your code is okay, thats the right way to do this. Anyhow, there are some misunderstandings:

1. fetchUserData.cfm does not contain key/value pairs. So it doesn't make sense to address keys in mData. Just use mData[index]

2. dataTables expects some more info from your serverside. At least you should tell datatables how many items in total are on your serverside and how many are filtered. I just hardcoded this info to your data. You should get the right values from counts in your server sided script.

   {
    "iTotalRecords":"6",
    "iTotalDisplayRecords":"6",
     "aaData": [
   [
       "1",
       "sameek",
       "sam",
       "sam",
       "[email protected]",
       "1",
       ""
   ],...
   

3. If you have the column names already set in the html part, you don't need to add sTitle.

4. The mRender Function takes three parameters:

   • data = The data for this cell, as defined in mData
   • type = The datatype (can be ignored mostly)
   • full = The full data array for this row.

So your mRender function should look like this:

  "mRender": function(data, type, full) {
    return '<a class="btn btn-info btn-sm" href=#/' + full[0] + '>' + 'Edit' + '</a>';
  }

Find a working Plunker here

var table =$('#example').DataTable( {
    data: yourdata ,
    columns: [
        { data: "id" },
        { data: "name" },
        { data: "parent" },
        { data: "date" },

        {data: "id" , render : function ( data, type, row, meta ) {
              return type === 'display'  ?
                '<a href="<?php echo $delete_url;?>'+ data +'" ><i class="fe fe-delete"></i></a>' :
                data;
            }},
    ],
    }
}

take a look here... this was very helpfull to me https://datatables.net/examples/ajax/null_data_source.html

$(document).ready(function() {
    var table = $('#example').DataTable( {
        "ajax": "data/arrays.txt",
        "columnDefs": [ {
        "targets": -1,
        "data": null,
        "defaultContent": "<button>Click!</button>"
    } ]
} );

$('#example tbody').on( 'click', 'button', function () {
    var data = table.row( $(this).parents('tr') ).data();
    alert( data[0] +"'s salary is: "+ data[ 5 ] );
    } );
} );

I contribute with my settings for buttons: view, edit and delete. The last column has data: null At the end with the property defaultContent is added a string that HTML code. And since it is the last column, it is indicated with index -1 by means of the targets property when indicating the columns.

//...
columns: [
    { title: "", "data": null, defaultContent: '' }, //Si pone da error al cambiar de paginas la columna index con numero de fila
    { title: "Id", "data": "id", defaultContent: '', "visible":false },
    { title: "Nombre", "data": "nombre" },
    { title: "Apellido", "data": "apellido" },
    { title: "Documento", "data": "tipo_documento.siglas" },
    { title: "Numero", "data": "numero_documento" },
    { title: "Fec.Nac.", format: 'dd/mm/yyyy', "data": "fecha_nacimiento"}, //formato
    { title: "Teléfono", "data": "telefono1" },
    { title: "Email", "data": "email1" }
    , { title: "", "data": null }
],
columnDefs: [
    {
        "searchable": false,
        "orderable": false,
        "targets": 0
    },
    { 
      width: '3%', 
      targets: 0  //la primer columna tendra una anchura del  20% de la tabla
    },
    {
        targets: -1, //-1 es la ultima columna y 0 la primera
        data: null,
        defaultContent: '<div class="btn-group"> <button type="button" class="btn btn-info btn-xs dt-view" style="margin-right:16px;"><span class="glyphicon glyphicon-eye-open glyphicon-info-sign" aria-hidden="true"></span></button>  <button type="button" class="btn btn-primary btn-xs dt-edit" style="margin-right:16px;"><span class="glyphicon glyphicon-pencil" aria-hidden="true"></span></button><button type="button" class="btn btn-danger btn-xs dt-delete"><span class="glyphicon glyphicon-remove glyphicon-trash" aria-hidden="true"></span></button></div>'
    },
    { orderable: false, searchable: false, targets: -1 } //Ultima columna no ordenable para botones
], 
//...

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