title: Could I make a column in a table only allows one 'true' value and all other rows should be 'false'
body: <p>In MySQL, Can I put a restriction like below at database level?</p>
  
  <p>I need to make sure 
  1. a specific column can only take either 'true' or 'false' values.
  2. and exactly only one row should be having 'true' value?</p>