For data management and database analysis, a data domain refers to all the unique values which a data element may contain. The rule of determining the domain boundary may be as simple as a data type with an enumerated list of values.

For example, a database table that has information about people, with one record per person, might have a " Gender " column. This gender column might be declared as a string data type and allowed to have one of two known code values : "M" for male and "F" for female and NULL for unknown gender. The data domain for the gender column: "M", "F".