title: Group values from a few rows into an array
body: <p>I'm using presto, and I have a dataset of rows with ids and values, each id can have multiple rows with multiple values. </p>
  
  <p>I need to group the values into an array and create one row of "value"s for each "id" (a comma delimited string of all values per id). </p>
  
  <p>The number of values for each id can be different (some will have 1, some will have ~10)
  Any ideas on how to do that?</p>