Bootstrap 4

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.2/css/bootstrap.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootswatch/3.3.7/flatly/bootstrap.min.css">
<div class="topTable row ">
  
  <div class="col-md-4 col-lg-3 col-sm-4 col-6">
      <form class="form-inline">
          <div class="form-group" style="width:100%;max-width:200px;">
            <div class="input-group" style="width:100%">
                <select class="form-control"  >
                    <option >All</option>
                    <option >Option1</option>
                     <option >Option1</option>
                      <option >Option1</option>
                  </select>
                 
            </div>
  </div>
  
  <!-- changes -->
  </div>
  </div>
  <div class="content">
  <div class="col-md-12">
  <!-- ./changes -->

 <div class="container-fluid">
   <div class="col-md-12">
<div class="col-md-12 tableDiv"  >
  <div class="constrained"  >
    <table class="table table-striped col-md-12 table-condensed cf" >
      <thead class="table-bordered cf">
        <tr>
          <th>Column1</th>
          <th>Column2</th>
          <th>Column3</th>
          <th>Column4</th>
          <th>Column5</th>
          <th>Column6</th>
        
        </tr>
      </thead>
      <tbody >
        <tr>
          <td > asdf</td>
          <td >asdfa</td>
          <td >fsdf</td>
          <td>sdfsfd</td>
          <td>sdfs</td>
          <td>fsdfsdf</td>
        </tr>
            <tr>
          <td > asdf</td>
          <td >asdfa</td>
          <td >fsdf</td>
          <td>sdfsfd</td>
          <td>sdfs</td>
          <td>fsdfsdf</td>
        </tr>
            <tr>
          <td > asdf</td>
          <td >asdfa</td>
          <td >fsdf</td>
          <td>sdfsfd</td>
          <td>sdfs</td>
          <td>fsdfsdf</td>
        </tr>
           ...

CSS

.topTable{
    height:70px;
    background:red;
    margin-top:-20px;
    margin-bottom:20px;     
    display: flex;
    padding-left: 32px;
    border:1px solid rgba(0,0,0,.1);
    
    /* changes */
    width: 100%;
    position: fixed;
    z-index:1;
    /* ./changes */
}

.tableDiv{
  margin-top:50px
}