That's probably just a bad on my side. I may have originally set the columns to INT in the CREATE TABLE statement then changed it to TINYINT and forgot to adjust the corresponding ALTER TABLE statement. The NOT NULL is added after the fact because until the column is populated with data during the build, it can be NULL, but after it shouldn't be. It allows for error checking (if any values get missed during population) and allows for a developer to know that the column should always contain data when looking at the table definition.