title: SQL JOIN - WHERE clause vs. ON clause
body: <p>After reading it, this is <em>not</em> a duplicate of <a href="https://stackoverflow.com/questions/44917/explicit-vs-implicit-sql-joins">Explicit vs Implicit SQL Joins</a>.
  The answer may be related (or even the same) but the <strong>question</strong> is different.</p>
  
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  <p>What is the difference and what should go in each?</p>
  
  <p>If I understand the theory correctly, the query optimizer should be able to use both interchangeably.</p>