title: SQL Join Return Null Without Duplicates
body: <p>I need to join the following tables to create the below desired result:</p>
  <p>Table A</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>id_1</th>
  <th>id_2</th>
  <th>foo1</th>
  <th>foo2</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>123</td>
  <td>456</td>
  <td>abc</td>
  <td>def</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>Table B</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>id_1</th>
  <th>id_2</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>123</td>
  <td>456</td>
  </tr>
  <tr>
  <td>123</td>
  <td>789</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>Current Result (duplicates)</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>id_1</th>
  <th>id_2</th>
  <th>foo1</th>
  <th>foo2</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>123</td>
  <td>456</td>
  <td>adb</td>
  <td>def</td>
  </tr>
  <tr>
  <td>123</td>
  <td>789</td>
  <td>abc</td>
  <td>def</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>The issue is that items foo1=adc and foo2=def do not correspond to id_2=789, and the join is creating duplicate line items for foo1 and foo2 because of the shared id_1.</p>
  <p>Ideal Result (null, without duplicates)</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>id_1</th>
  <th>id_2</th>
  <th>foo1</th>
  <th>foo2</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>123</td>
  <td>456</td>
  <td>adb</td>
  <td>def</td>
  </tr>
  <tr>
  <td>123</td>
  <td>789</td>
  <td>null</td>
  <td>null</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I've tried iterations of left, inner, and outer joins, to no avail.</p>