title: Get unique symmetric pairs from two columns with SQLite
body: <p>I have been looking at similar questions on Stack but any of them seems to be helpful to me. I have the following table called "Likes":</p>
  
  <pre><code> ID1    ID2
  1689    1709
  1709    1689
  1782    1709
  1911    1247
  1247    1468
  1641    1468
  1316    1304
  1501    1934
  1934    1501
  1025    1101
  </code></pre>
  
  <p>I want to get the unique pairs between the two columns ID1 and ID2. That is:</p>
  
  <pre><code> ID1    ID2
  1689    1709
  1501    1934
  </code></pre>
  
  <p>Any idea? Thx.</p>