title: How to change datatype of primary key field in mysql workbench?
body: <p>In mysql workbench, I created a new table and added a column <code>id</code>, and by default its datatype is set to <code>INT</code>, <code>PK</code> and <code>NN</code> boxes are  selected. When I tried to change the datatype of <code>id</code> column to <code>VARCHAR()</code>, it gave the following error:</p>
  
  <p><img src="https://i.stack.imgur.com/rYtFL.jpg" alt="enter image description here"></p>
  
  <p>What is wrong?</p>