DBMS Interviews and Answers Part-4
31:What is DML Compiler?
ANSWER:
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.
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?
What is Query evaluation engine?
ANSWER:
It executes low-level instruction generated by compiler.
It executes low-level instruction generated by compiler.
33:
What is DDL Interpreter?
What is DDL Interpreter?
ANSWER:
It interprets DDL statements and record them in tables containing metadata.
It interprets DDL statements and record them in tables containing metadata.
34:
What is Record-at-a-time?
What is Record-at-a-time?
ANSWER:
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.
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?
What is Set-at-a-time or Set-oriented?
ANSWER:
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.
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?
What is Relational Algebra?
ANSWER:
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.
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?
What is Relational Calculus?
ANSWER:
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.
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
How does Tuple-oriented relational calculus differ from domain-oriented relational calculus
ANSWER:
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL
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?
What is normalization?
ANSWER:
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
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?
What is Functional Dependency?
ANSWER:
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.
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.