Relational calculus was a theory formulated by Edgar. F. Codd to produce a declarative database query language. His idea was that the user need not be concerned about the structure of data in the system. It directly specifies what is to be retrieved rather than how to retrieve information, making it easier for non-experts to use it. It establishes and exploits a relationship between the different entities in the table to answer the query put into the database.
Most organizations have a database with all kinds of information. For instance, a business organization would have a table with details of customers’ names, address and phone numbers. Another table would have details of an order placed by the customer such as product, quantity, unit price and delivery dates. The presence of a relational calculus program in the system enables a view of the data as per the user’s needs. For instance, a sales officer can obtain a report of all transactions made on a certain date. The finance manager can retrieve information regarding pending payments of customers.
Relational calculus comes in two forms: tuple and domain relational calculus. A tuple is usually an ordered set of values in a row in a database. Tuple relational calculus address queries like finding out details of a staff earning more than a basic salary. A domain uses values from an attribute’s domain area, like the columns. Domain relational calculus answers queries like names of managers who earn more than the basic salary.
Using relational calculus in a database management system is beneficial since it is easy to use. It is flexible enough to allow operators to extract information from various tables and link them up to provide desired output. Use of relational calculus provides a “relational” view of the data rather than a graphical output which makes it advantageous to a user who is unfamiliar with programming.