Dynamic Dropdown and Print Values?

I'm doing a BI panel, and in it I'm looking for all NETWORKS and putting it inside a dropdown,

Follow the code below:

<div class="row wow fadeInRight">
                        <div class="col-sm-3 col-sm-offset-2">
                            <form action="#">
                                <div class="form-group">
                                    <label id="drops-labels"><b id="centraliza-txt">REDE</b></label>
                                        <span data-toggle="tooltip" data-placement="top" title="ESCOLHA A REDE">
                                            <?php
                                                echo "<select class='form-control input-sm' name='redes' id='rede'>";
                                                    echo "<option value='0'>--Selecione--</option>";
                                                while($dadosRedes = mysql_fetch_array($buscarDadosSuperv)) {
                                                    echo "<option value='".$dadosRedes['Rede']."'>".$dadosRedes['Rede']."</option>";
                                                    }
                                                echo "</select>";
                                            ?>
                                        </span>
                                </div>
                            </form>
                        </div>

However, I have another dropdown that I want to be populated from a select in my database, bringing all the STORES of this respective NET .

<div class="col-sm-3">
                            <form action="#">
                                <div class="form-group" id="load_lojas">
                                    <label id="drops-labels"><b id="centraliza-txt">LOJA</b></label>
                                    <span data-toggle="tooltip" data-placement="top" title="ESCOLHA A LOJA">
                                        <select class="form-control input-sm" name="loja" id="loja">
                                            <option value="0">--Selecione--</option>
                                        </select>
                                </div>
                            </form>
                        </div>

I tried to do with Ajax and Jquery and nothing.

And after that, I want to populate the values found in a table by making a select in my table, filtering by NET and SHOP .