Data domain

In data management and database analysis, a data domain refers to all the values which a data element may contain. The rule for 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, "F" for female—and NULL for records where gender is unknown or not applicable (or arguably "U" for unknown as a sentinel value). The data domain for the gender column is: "M", "F".