title: Summing the length of a varchar
body: <p>I have two tables that look something like this:</p>
  
  <p>Checkpoint with field:</p>
  
  <pre><code>  Checkpoint_id
    Checkpoint_name
  </code></pre>
  
  <p>checkpoint_id is a primary key</p>
  
  <p>Checkpoint_data with fields:</p>
  
  <pre><code>Checkpoint_id
  sequence_number
  data
  </code></pre>
  
  <p>(checkpoint_id, sequence_number) is the primary key</p>
  
  <p>What I want to do, is get the checkpoint_id with its name, but also sum the length of all of the data that is linked via checkpoint_id. For example, I would want to get the length of sequence_number 1, 2, 3 and 4, and then add up the lengths off all of data and return it with the corresponding checkpoint id and name. The data field is a varchar</p>