Database Management System2015RELATIONAL ALGEBRARelational algebra is a procedural query language, which takes instances of relations asinput and yields instances of relations as output. It uses operators to perform queries. Anoperator can be eitherunaryorbinary. They accept relations as their input and yield relationsas their output. Relational algebra is performed recursively on a relation and intermediate resultsare also considered relations.The fundamental operations of relational algebra are as follows −SelectProjectUnionSet differentCartesian productRenameJoinsJoinis a combination of a Cartesian product followed by a selection process. A Join operationpairs two tuples from different relations, if and only if a given join condition is satisfied.Join is used to fetch data from two or more tables, which is joined to appear as single set of data. SQLJoin is used for combining column from two or more tables by using values common to both tables. JoinKeyword is used in SQL queries for joining two or more tables. Minimum required condition for joiningtable, is (n-1) where n, is number of tables. Atable can also join to itself known as, Self Join. Join are oftwo types:Theta JoinNatural JoinTheta (θ) joinTheta R1⋈θR2R1 and R2 are relations having attributes (A1, A2, .., An) and (B1, B2,.. ,Bn) such that theattributes don’t have anything in common, that is R1 ∩ R2 = Φ.Theta join can use all kinds of comparison operators.