Friday, 6 February 2015

relational database management system interview questions and answers (Page 4)

31. What is DML Compiler? | RDBMS Questions
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

32. What is Query evaluation engine? | RDBMS Questions
It executes low-level instruction generated by compiler.

33. What is DDL Interpreter? | RDBMS Questions
It interprets DDL statements and record them in tables containing metadata.

34. What is Record-at-a-time? | RDBMS Questions
The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

35. What is Set-at-a-time or Set-oriented? | RDBMS Questions
The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

36. What is Relational Algebra? | RDBMS Questions
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.

37. What is Relational Calculus? | RDBMS Questions
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.

38. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus. | RDBMS Questions
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.

39. What is normalization? | RDBMS Questions
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
? Minimizing redundancy
? Minimizing insertion, deletion and update anomalies.

40. What is Functional Dependency? | RDBMS Questions
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.
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