What Do You Know About Relational Algebra & Relational Calculus?


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Muhammad Azhar Profile
Muhammad Azhar answered
Relational Algebra is a theoretical language. The relational algebra is not a user friendly language. Relational algebra defines relational operators that are used to perform various operations on relations. Relations can be manipulated using these operators to achieve desired results.

Relational algebra is not directly used in commercial database processing, because no commercial DBMS product provides relational algebra facilities. The relational algebra helps to learn SQL because the syntaxes of SQL statements are similar to syntax of relational algebra expressions.Relational algebra consists of a collection of operators used to perform various operations on the relations of database.

The relational algebra operators combined. With relations and form a relational algebra expression, which also returns a relation. The syntax of expression of relational algebra is very simple. A relational algebra operator takes one or two relations as operands and returns a single relation as result. Both the operands and returned results are tables.
In relational algebra, relational operators are:
(a)        The select operator
(b)      The project operator
(c)        Set operators (I)        Union (ii)      Difference (iii)    Intersection
(iv)      Cartesian product

Relational Calculus:
Relational calculus is a non-procedural relational data manipulation language in which user simply specifies what data should be retrieved, but not how to retrieve the data. The relational calculus is a formal query language. It is not related to the differential and integral calculus. The relational calculus is not easy to learn and to use. It is not used in commercial database processing.

Domain relational calculus is another type of relational calculus. In this type of relational calculus, the variables are used that take their values from domains instead of tuples of relations.

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