title: Does LIMIT 1 have any performance boost?
body: <p>Does appended <code>LIMIT 1</code> after query have any performance boost?</p>
  
  <p>...if there could be only one possible entry that matched (<code>WHERE</code> clause for primary key)?</p>
  
  <pre><code>SELECT `x`
  FROM `unicorns`
  WHERE `id` = 123
  LIMIT 1
  </code></pre>
  
  <p>...the same, but now it's <code>DELETE</code>:</p>
  
  <pre><code>DELETE FROM `unicorns`
  WHERE `id` = 123
  LIMIT 1
  </code></pre>
  
  <p>...and <code>UPDATE</code>:</p>
  
  <pre><code>UPDATE `unicorns`
  SET `rainbows` = `rainbows` + 1
  WHERE `id` = 123
  LIMIT 1
  </code></pre>
  
  <p>P.S. Column <code>id</code> is primary key so it's unique.</p>
  
  <p>Thanks in an advice!</p>