title: Retrieve MIN and MAX date in one query
body: <p>I have in a mysql database a table "travel_data" with three relevant columns:</p>
  
  <pre><code>+--------------------------+
  | from  | to   | date      |
  +--------------------------+
  |City1 | City2 | 2015-12-12|
  |City3 | City4 | 2016-12-12|
  |City1 | City2 | 2015-06-06|
  |City3 | City4 | 2017-01-01|
  +--------------------------+
  </code></pre>
  
  <p>(plus a few other colums  that I don't need at the moment).</p>
  
  <p>I'm looking for a query that allows me to get, in one query if possible, the first and last date for each itinerary per row, i.e. something like:</p>
  
  <pre><code>+------------------------------------------------+
  |from  | to    | firstTravelDate | LastTravelDate|
  +------------------------------------------------+
  |City1 | City2 | 2015-06-06      | 2015-12-12    |
  |City3 | City4 | 2016-12-12      | 2017-01-01    |
  +------------------------------------------------+
  </code></pre>
  
  <p>I've search for "mysql select maximum minimum in one query" but solutions from there, inasfar as they worked at all, returned mix/max per table; I need the min/max per possible combination of from/to. This has me baffled to an extent where I haven't even a start for a working query. This needs to run only on MySql, so a standards-compliant solution is not necessary.</p>
  
  <p>(Improvements on the title are welcome, I don't feel the title fully covers the actual question). </p>