DB2® supports a number of built-in data types. It also provides support for user-defined data types. Figure 1 shows the supported built-in data types.
All data types include the null value. The null value is a special value that is distinct from all non-null values and thereby denotes the absence of a (non-null) value. Although all data types include the null value, columns defined as NOT NULL cannot contain null values.
A Unicode database also supports national character strings which are synonyms for graphic strings.