Difference between Relational Algebra and Relational Calculus

Relational Algebra and Relational Calculus are two preliminarily important topics in the study of DBMS. Both are standardized query languages used for querying databases but the two have different approaches and operations. Relational Algebra is imperative as it deals mainly with how the data is to be obtained whereas Relational Calculus is imperative-free as it is concerned with which data is to be obtained but not how. Knowledge of the differences between these two is critical to database professional as it impacts the way they design databases and optimize their queries.

What is Relational Algebra?

Relational Algebra is a procedural language. In Relational Algebra, The order is specified in which the operations have to be performed. In Relational Algebra, frameworks are created to implement the queries. The basic operations included in relational algebra are: 

1. Select (σ)
2. Project (Π)
3. Union (U)
4. Set Difference (-)
5. Cartesian product (X)
6. Rename (ρ) 

Advantages of Relational Algebra

• Simplicity and Precision: On the same note, Relational Algebra offers a simple and efficient methodology for how questions can be framed especially for a layman who has a crystal-clear understanding of the entire method.
• Optimization Potential: It makes optimization possible due to the procedural aspect, and shows how one can find the best way to execute the statement.
• Foundational for SQL: Most of the SQL commands can be traced to the Relational Algebra operations as will be seen from the following sections.

Disadvantages of Relational Algebra

• Complex for Complex Queries: Relational algebra is more or less effective when the query is highly complex because with increasing complexity, Relational Algebra analysis in full becomes a cumbersome exercise.
• Less Abstract: It is also procedural and thus it forces users to detail out the procedure of data access, which may not be easily understood by end users who are not very conversant with databases.

What is Relational Calculus?

Relational Calculus is the formal query language. It is also known as Declarative language. In Relational Calculus, the order is not specified in which the operation has to be performed. Relational Calculus means what result we have to obtain. 
Relational Calculus has two variations: 

1. Tuple Relational Calculus (TRC)
2. Domain Relational Calculus (DRC)

Relational Calculus is denoted as:  

{ t | P(t) }

Where,
t: the set of tuples
p: is the condition which is true for the given set of tuples.

Advantages of Relational Calculus

• Higher Abstraction: Relational Calculus enables a user to tell what information is needed but not how it needs to be retrieved which makes it easier to express yourself.
• User-Friendly for Non-Experts: This form is easier for the users who may not know the steps that have to be taken when formulating queries.

Disadvantages of Relational Calculus

• Less Optimizable: It can be said that this is a disadvantage of the ALG, as being non-procedural, it does not produce definite recommendations to be followed in optimization of a query, which is likely to result in inferior query processing.
• Potentially Ambiguous: The abstract nature can at time make it difficult to get the sense of interpretation on the query side and therefore predict results.

Difference Between Relational Algebra and Relational Calculus

Conclusion

Relational Algebra and Relational Calculus are two important query languages in Database management and have their perquisites and demerits. What is more, Relational Algebra presents the procedural approach to query processing that can be effectively optimized, whereas Relational Calculus presents the approach more abstracted and the latter makes it easier to form the queries. The use of the acronyms though interchanges depends on the requirements of the database system as well as the capacity of the users.