title: Conditions in LEFT JOIN (OUTER JOIN) vs INNER JOIN
body: <pre><code>SELECT A.COL1, B.COL1,C.COL1
  FROM TABLEA A
  LEFT JOIN TABLEB B ON A.COL1 = B.COL1
  LEFT JOIN TABLEC C ON (
          C.COL3 IS NOT NULL
          AND (
                C.COL2 = 664
                AND A.COL1 = C.COL1
          )
  )
  </code></pre>
  
  <p>In regards to technicalities of SQL, what does the condition written in parentheses after <code>LEFT JOIN TABLE C ON</code> mean? Why are those necessary?</p>