title: SQL inner vs left join question
body: <p>I have a very badly performing sql query.  I tracked it down to the INNER JOIN performed on the table.  Changing this to LEFT join significantly increases performance (from 6 min to 20 sec) - now i know the 2 are not equiv, but... here is what i am asking</p>
  
  <pre><code>SELECT * 
    FROM SomeTable ST
    JOIN BigTable BT ON BT.SomeID = ST.SomeID 
                    AND BT.Something = ST.Something 
                    AND BT.AnotherValue = '123'
  </code></pre>
  
  <p>Since the join has additional criteria (and something=something) -- is changing this to a left join producing the same results - but MUCH faster?</p>
  
  <p>The results returned are the same using LEFT/INNER with left being significantly faster... </p>