title: SQL group values for one column by another column
body: <p>Is there some kind of "aggregate" function in SQL that just turns values into a list? An example might be a table of the form:</p>
  
  <pre><code>| game_id | player | score |
  |---------|--------|-------|
  |   1     | fred   | 2     |
  |   1     | tom    | 1     |
  |   2     | fred   | 3     |
  |   2     | tom    | 4     |
  </code></pre>
  
  <p>What I would like returned is a table that looks like this:</p>
  
  <pre><code>| player | scores |
  |--------|--------|
  |   fred | 2, 3   | 
  |   tom  | 1, 4   |
  </code></pre>
  
  <p>The command might look something like:
  <code>SELECT player, listify(score) FROM games GROUP BY player;</code></p>