title: Find overlapping dates
body: <p>I'm looking voor a solution for the next question. </p>
  
  <p>In a table i have subscriptions with a:</p>
  
  <pre><code>~start_date~, ~end_date~, ~paid_till_date~
  </code></pre>
  
  <p>These subscriptions also have a ~person_id~. </p>
  
  <p>Im looking to build a query to find the subscriptions for persons who have paid double for the same days and i would like the double payed subscriptions in the result of the query. Can somebody Help? </p>
  
  <p>For example: </p>
  
  <pre><code>person_id '2' has 2 subscriptions 
  </code></pre>
  
  <p>Subscription:1 </p>
  
  <pre><code>Start_date **2017-06-30**, End_date **2017-07-14**, Paid_till_date **2017-07-07** 
  </code></pre>
  
  <p>Subscription:2 </p>
  
  <pre><code>Start_date **2017-07-03**, End_date **2017-07-17**, Paid_till_date **2017-07-10** 
  </code></pre>
  
  <p>These subscriptions overlap and '2' wil pay double for a few days.</p>
  
  <p>So if this is the only person_id who payed double for a few days these 2 subscriptions should be the result of the query.</p>