Domain Relational Calculus in DBMS

DRC in DBMS 

• In Domain relational calculus filtering of records is done based on the domain of the attributes rather than tuple values 
• A domain is nothing but the set of allowed values in the column of a table 

Syntax: 

{ c1, c2, c3, ..., cn | F(c1, c2, c3, ... ,cn)} 

where, c1, c2… etc represents the domain of attributes(columns) and F represents the formula including the condition for fetching the data. 

Example 1

{< name, age > | ∈ Student ∧ age <21} 

Again, the above query will return the names and ages of the students in the table Student who not greater than 21 years old 

Example 2

{< Fname, Emp_ID > | ∈ Employee ∧ Salary > 10000} 

The result here will be returning the Fname and Emp_ID values for all the rows in the employee table where salary is greater than 10000.