title: Joining to a table with multiple entries for just one record
body: <p>I have a table called <code>geo</code>.</p>
  <p>I am joining to this table like so -</p>
  <pre><code>JOIN geo ON other_table.county_geoid = geo.geoid
  </code></pre>
  <p>This is sample data in the table -</p>
  <pre><code>id  type    state  county       stcode  county_code geoid
  539 COUNTY  CA     Los Angeles  05      210         06037
  538 COUNTY  CA     Los Angeles  05      200         06037
  520 COUNTY  CA     Alameda      05      000         06001
  </code></pre>
  <p>How do I join to this table so records where the county is <code>Los Angeles</code> aren't counted twice?</p>