Data domain

In data management and database analysis, a data domain is the collection of values that 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.^[1]

For example, a

code values: "M" for married, "S" for single, and NULL

for records where marital status is unknown or not applicable. The data domain for the marital status column is: "M", "S".

In a normalized data model, the reference domain is typically specified in a reference table. Following the previous example, a Marital Status reference table would have exactly two records, one per allowed value—excluding NULL. Reference tables are formally related to other tables in a database by the use of foreign keys.

Simple domain boundary rules, if database-enforced, may be implemented through a check constraint or, in more complex cases, in a database trigger. For example, a column requiring positive numeric values may have a check constraint declaring that the values must be greater than zero.

This definition combines the concepts of domain as an area over which control is exercised and the mathematical idea of a

independent variable for which a function is defined, as in Domain of a function

.

References

ISBN 978-0-12-455840-3
. Retrieved 19 August 2011.

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[1] ISBN 978-0-12-455840-3
. Retrieved 19 August 2011.

[1]

See also

References