title: How to create a "unique" constraint on a boolean MySQL column?
body: <p>I would like to add a <code>BOOLEAN</code> column to a MySQL table which will be named <code>is_default</code>. In this column, only one record can have <code>is_default</code> set to <code>true</code>.</p>
  
  <p>How can I add this constraint to my column with MySQL?</p>
  
  <p>Thanks!</p>
  
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  <p>UPDATE</p>
  
  <p>If it is not a constraint that I should add. How are we dealing with this type of problem on DBs?</p>