title: MySQL: update single table one column data to another column
body: <p>I have a MySQL table called <code>Cars</code>. The <code>Cars</code> table has three columns: <code>id int auto increment</code>, <code>foo varchar(255)</code>, <code>bar varchar(255)</code>.</p>
  
  <p>I want to simply update all rows in the Cars table into the <code>bar</code> column with the same value from <code>foo</code> if <code>foo</code> is not null. So both foo and bar will have the same value after the update wherever foo is not null.</p>