title: MySQL InnoDB: Difference Between `FOR UPDATE` and `LOCK IN SHARE MODE`
body: <p>What is the exact difference between the two locking read clauses:</p>
  
  <pre><code>SELECT ... FOR UPDATE
  </code></pre>
  
  <p>and</p>
  
  <pre><code>SELECT ... LOCK IN SHARE MODE 
  </code></pre>
  
  <p>And why would you need to use one over the other?</p>