title: Show all relationships between two columns in MySQL
body: <p>I have a single table that has data like the following:</p>
  
  <p>Column 1 -- Column 2</p>
  
  <p>A -- Z</p>
  
  <p>A -- Y</p>
  
  <p>B -- Y</p>
  
  <p>I am looking for a way in MySQL to roll up this data so that I get the following table that will show group associations:</p>
  
  <p>Column 1 -- Column 2</p>
  
  <p>A,B -- Z,Y</p>
  
  <p>I can use the group_concat function to get one column at a time grouped together, but I need both columns to be grouped to show the relationships.  Any advice is greatly appreciated!</p>