Name and data type are the most basic properties of a column, but many other properties can be defined for a column. You do not have to specify these properties to be able to create the columns, but you can use them to further refine the type of data that can be stored within a column. Note that many of the available column properties relate to indexes and constraints that are beyond the scope of this section. The following sections describe some of the column properties you are most likely to encounter.
When you are defining tables, it is always good idea to explicitly state whether a column should or should not contain nulls. You do this by specifying the
NOT NULL keywords after the ...