Mysql WorkBench：默认varchar值为空

Before I started using MySql WorkBench, I was using phpmyadmin and liked to set default values of varchars to empty. So in my code I would not have to check for null values and could only use if $value = '' comparisions. How do I put default value as empty in mysql workbench? If i leave the text box empty unlike phpmyadmin it think i do not want any default value.Before I started using MySql WorkBench, I was u