title: Why SELECT ... WHERE last_name = 0 returns all rows?
body: <p>I've got a simple table in MySQL:</p>
  
  <pre><code>create table t_users(
      user_id INT NOT NULL AUTO_INCREMENT,
      first_name VARCHAR(100) NOT NULL,
      last_name  VARCHAR(100) NOT NULL,
  PRIMARY KEY(user_id));
  </code></pre>
  
  <p>I'm puzzled to discover that the following query returns ALL rows:</p>
  
  <pre><code>SELECT first_name, last_name
  FROM t_users
  WHERE last_name = 0;
  </code></pre>
  
  <p>Can someone explain that?
  Thank you! </p>