title: Sql ONLY keyword
body: <p>In SQL grammar I found strange rule that suggest that <code>select * from ONLY (t1)</code> is valid SQL.</p>
  
  <p>My question is: what does <code>ONLY</code> mean in this context?</p>
  
  <p>It is in "7.6 table reference" section of spec:</p>
  
  <pre><code>&lt;table primary&gt; ::=
             &lt;table or query name&gt; [ [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ] ]
       |     &lt;derived table&gt; [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ]
       |     &lt;lateral derived table&gt; [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ]
       |     &lt;collection derived table&gt; [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ]
       |     &lt;table function derived table&gt; [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ]
       |     &lt;only spec&gt; [ [ AS ] &lt;correlation name&gt; [ &lt;left paren&gt; &lt;derived column list&gt; &lt;right paren&gt; ] ]
       |     &lt;left paren&gt; &lt;joined table&gt; &lt;right paren&gt; 
  
  &lt;only spec&gt; ::= ONLY &lt;left paren&gt; &lt;table or query name&gt; &lt;right paren&gt; 
  </code></pre>