title: SQLAlchemy: Selecting one row for each distinct value of a column
body: <p>I want to select one row each for <strong>each distinct value of a column</strong>. Here I want to perform it for <code>col1</code>: </p>
  
  <pre><code>| ID | COL1 | COL2 |
  --------------------
  |  1 |    0 |    0 |
  |  2 |    0 |    1 |
  |  3 |    1 |   11 |
  |  4 |    1 |   12 |
  |  5 |    1 |   16 |
  </code></pre>
  
  <p>Which results in:    </p>
  
  <pre><code>| ID | COL1 | COL2 |
  --------------------
  |  1 |    0 |    0 |
  |  3 |    1 |   11 |
  </code></pre>
  
  <p>as <code>0</code> and <code>1</code> were the distinct values for <code>col1</code>. I am not strict about which row is returned (no need of least value of id, for example) as long as distinct values of column is returned.</p>
  
  <p>Please assume the model is called <code>TestModel</code> and everything is fully mapped.</p>