Null values are different than any other value in the world, you cannot use the qual operator when working with null values, query like this will not work:
Saturday, November 19, 2016
Sunday, November 13, 2016
When first starting a project, you probably just creating a few tables inside a database, but as the project gets more mature, the application is growing and you end up having so many tables. On mysql you can count the number of tables inside a database with a special query.