title: What is the difference when comparing with parentheses: WHERE (a, b)=(1,2)
body: <p>I stumbled across the follwoing (valid) query in MySQL (also works in Oracle/MSSQL when replacing <code>=</code> with <code>IN</code>):</p>
  
  <pre><code>SELECT * from mytable WHERE (a, b)=(1,2)
  </code></pre>
  
  <p>It's the same as</p>
  
  <pre><code>SELECT * from mytable WHERE a=1 and b=2
  </code></pre>
  
  <p>I think the definition in the <a href="https://dev.mysql.com/doc/refman/5.7/en/expressions.html">MySQL docs</a> is here:</p>
  
  <pre><code>simple_expr:
    [...]
    | (expr [, expr] ...)
    [...]
  </code></pre>
  
  <p>What is this called? Are there any pros and cons for using it?</p>