34.  What is Relational Algebra?

It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.


35.  What is Relational Calculus?

It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.


36.  How does Tuple-oriented relational calculus differ from domain-oriented relational calculus

The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL

The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.


37.  What is normalization?

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties

Ø      Minimizing redundancy

Ø      Minimizing insertion, deletion and update anomalies.  


38.  What is Functional Dependency?  

A Functional dependency is denoted by X     Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.


39.  When is a functional dependency F said to be minimal?

Ø      Every dependency in F has a single attribute for its right hand side.

Ø      We cannot replace any dependency X    A in F with a dependency Y   A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.

Ø      We cannot remove any dependency from F and still have set of dependency that is equivalent to F.


40.  What is Multivalued dependency?

Multivalued dependency denoted by X        Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

Ø      t3[x] = t4[X] = t1[X] = t2[X]

Ø      t3[Y] = t1[Y] and t4[Y] = t2[Y]

Ø      t3[Z] = t2[Z] and t4[Z] = t1[Z] 

where [Z = (R-(X U Y)) ]


41.  What is Lossless join property?

It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.