Domain Constraints in DBMS

Domain constraints in DBMS

In this article, we will learn about Domain Constraints in DBMS.

  • DBMS table is viewed as a combination of rows and columns. 
  • For example, if you are having a column called month and you want only [Jan, Feb, March….dec] as values allowed to be entered for that particular column which is referred to as domain for that particular column that.

Definition :

Domain constraint ensures  two things 

    • It makes sure that the data value entered for that particular column matches with the data type defined for that column 
    • It shows that the constraints((NOT NULL / UNIQUE / PRIMARY KEY / FOREIGN KEY / CHECK / DEFAULT)) impose on that column not fulfilled or not 
Domain Constraints in DBMS

Domain Constraint = data type check for the column + Constraints (NOT NULL / UNIQUE / PRIMARY KEY / FOREIGN KEY / CHECK / DEFAULT)

Example :

For example, we want to create a table “student” with “stu_id” field having a value greater than 100,  can create a domain and table like this:

create domain id_value int
constraint id_test
check(value > 100);
create table student (
stu_id id_value PRIMARY KEY,
stu_name varchar(30),
stu_age int
);