title: Why do we have OUTER clause in LEFT JOIN?
body: <p>What the difference between the 2 queries below</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>This question is already answered in a similar question here <a href="https://stackoverflow.com/questions/406294/left-join-and-left-outer-join-in-sql-server">LEFT JOIN vs. LEFT OUTER JOIN in SQL Server</a>. </p>
  
  <pre><code>SELECT * FROM ca 
  LEFT JOIN exam 
  ON ca.subject = exam.subject
  </code></pre>
  
  <p>and</p>
  
  <pre><code>SELECT * FROM ca 
  LEFT OUTER JOIN exam 
  ON ca.subject = exam.subject
  </code></pre>
  
  <p>Tables</p>
  
  <pre><code>Table 'CA'
  --------------------
  subject|score
  ----------------
  ENG    |25
  MTH    |34
  BIO    |18
  
  
  Table 'Exam'
  --------------------
  subject|score
  ----------------
  ENG    |25
  </code></pre>
  
  <p>Running the 2 queries produce the same result in mysql, sqlserver 2008. I didn't test in Oracle.</p>
  
  <pre><code>subject | score1 | subject | score1
  --------------------------------------
  ENG       14       ENG       44
  MTH       28       NULL      NULL
  BIO       22       NULL      NULL
  </code></pre>
  
  <p>What's the purpose of that OUTER clause</p>