title: ER vs database schema diagrams
body: <p>when i search the web for er diagram and database schema these 3 diagram types found but all are named under er diagram.i want to know</p>
  
  <ul>
  <li><strong>what is database schema diagram and  what is er diagram</strong></li>
  <li><strong>why all are named under er diagram</strong></li>
  </ul>
  
  <p><a href="https://i.stack.imgur.com/4Hyfc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4Hyfc.png" alt="diagram 1"></a>
  <a href="https://i.stack.imgur.com/T0fPW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T0fPW.png" alt="diagram 2"></a>
  <a href="https://support.smartbear.com/support/media/images/support/kb/data/2011/1/31/info-database-schema.jpg" rel="nofollow noreferrer"><img src="https://support.smartbear.com/support/media/images/support/kb/data/2011/1/31/info-database-schema.jpg" alt="diagram 3"></a></p>