Domian is called the domain, that is, the range of X in f(x).

The Range is called range, that is, the whole range of f(x).

Domain (domain)

A domain is a set of values with the same data type, also called a range. Domain such as integer, real number and character set are all domain. The number of values contained in a field is called the cardinality of the field. In the relationship, the domain defines the value range of the attribute. The following is an example of a domain. There are three fields D 1, D2 and D3, which represent the collection of students' names, genders and ages. These fields are defined as: D 1={ Zhao Yi, Qian Er, Sun San}, radix m 1=3, {male, female}, radix m2=2, D3={ 18,19,20}.