title: Merge 2nd column for each 1st column in MySQL
body: <p>I have data that looks like</p>
  
  <pre><code>ABC     1234,2134,6754,7658
  XYZ     4324,5643,6754,9832,5478,0987
  DEF     2938,4637,1093,6734,5632
  GHI     3274
  ABC     9983
  DEF     1211,4782
  </code></pre>
  
  <p>What I want is to merge the 2nd column for each ID in 1st column</p>
  
  <pre><code>ABC     1234,2134,6754,7658,9983 
  XYZ     4324,5643,6754,9832,5478,0987
  DEF     2938,4637,1093,6734,5632,1211,4782
  GHI     3274
  </code></pre>
  
  <p>What I was thinking is programmatically iterate over each ID in 1st column (sorted). Continue for each ID until it doesn't match the next row. Can this be done with a SQL query instead. How can I go about it?. I have about 100k rows. Thanks  </p>