what is domain in dbms

In DBMS, a domain is a unique set of values that can be assigned to an attribute in a database. It is a data type definition that can either be a built-in type, such as an integer or a string, or a custom type that defines data constraints. A domain defines the permitted values for an attribute and ensures that the value taken by the attribute must be an atomic value from its domain. For example, a domain of strings can accept only string values, and a domain of integers can accept whole numbers that are negative, positive, and zero. Domain constraints are user-defined columns that help the user enter the value according to the data type, and if it encounters a wrong input, it gives a message to the user that the column is not fulfilled properly. To create a domain, the CREATE DOMAIN command is used in SQL. Domain constraints can be used to impose semantic constraints, and they can be used to assist the user in entering values that are appropriate for the data type.