title: Is it safe to omit the INNER keyword if I explicitly want to INNER JOIN?
body: <p>It’s not that important (please take note), but it’s a syntactical particularity and it’s about portability, and I didn’t find a question (or answer) quoting reliable resources or specifications, so I’m curious:</p>
  
  <p><strong>Is it <em>safe</em> to omit the <code>INNER</code> keyword if I explicitly want to <code>INNER JOIN</code>?</strong></p>
  
  <p>By “safe” I mean:</p>
  
  <ul>
  <li>It will work in both SQL Server 2000 and 2016.</li>
  <li>It will work in any other SQL flavor without the <code>FROM</code> clause needing adjustment.</li>
  <li>Its backward and forward compatibility is not just a sure bet.</li>
  <li>Its reliability is backed by being standard compliant.</li>
  </ul>
  
  <p>Regarding <code>INNER</code>, <a href="https://msdn.microsoft.com/en-us/library/ms177634.aspx" rel="noreferrer">MSDN docs</a> (for versions 2005 through 2014) say:</p>
  
  <blockquote>
    <p>When no join type is specified, this is the default.</p>
  </blockquote>
  
  <p>The <a href="http://www.postgresql.org/docs/8.0/static/sql-select.html#SQL-FROM" rel="noreferrer">PostgreSQL Documentation</a> implicitly notes:</p>
  
  <blockquote>
    <p><code>[ INNER ] JOIN</code></p>
  </blockquote>
  
  <p>I didn’t find a corresponding statement in the <a href="https://dev.mysql.com/doc/refman/5.0/en/join.html" rel="noreferrer">MySQL Reference Manual</a> nor while searching the web for Oracle or ANSI/ISO SQL, the latter being of particular interest.</p>