title: inner join vs left join - which is faster for the same result?
body: <p>If both inner join and left join can achieve the same result, which one is faster and has better performance (especially on large data)?</p>
  
  <p>inner join:</p>
  
  <pre><code>SELECT *
  FROM Table_A A
  INNER JOIN Table_B B
  ON A.PK_A = B.PK_B
  </code></pre>
  
  <p>left join:</p>
  
  <pre><code>SELECT *
  FROM Table_A A
  LEFT JOIN Table_B B
  ON A.PK_A = B.PK_B
  
  WHERE A.PK_A = B.PK_B
  </code></pre>
  
  <p>Table A:</p>
  
  <pre><code>PK_A    User
  1   FOX
  2   COP
  3   TAXI
  6   WASHINGTON
  7   DELL
  5   ARIZONA
  4   LINCOLN
  10  LUCENT
  </code></pre>
  
  <p>Table_B:</p>
  
  <pre><code>PK_B    Message
  1   TROT
  2   CAR
  3   CAB
  6   MONUMENT
  7   PC
  8   MICROSOFT
  9   APPLE
  11  SCOTCH
  </code></pre>
  
  <p>Any ideas? How can I test their performance on a large data?</p>