RDBMS Aptitude Question Answer 2016.
what is a domain?
the set of allowable value for the attribute is the domain of the attribute.
what is a tuple?
tuples are the members of a relation.an entity type having attributes can be
represented by set of these attributes called tuple.
what is a selection?
an operation that selects only some of the tuples in the relation is known as
selection operation.the selection operation yields a horizontal subset of a
what is a join operation?
the join operation allows the combination of two relations to form a new
waht are base operations in relational algebra?
the term of the relation as performed by combining the tuples from one
relation with those a second relation to produce a third
relation.duplicate tuples are eliminated.the the relation must be union
the difference of two relations is a third relation having tuples that occur in
the first relation but not in the second relation.
the intersection operation selects the common tuples from the two relations.
the cartesian product of two relations is the concatination of tuples belonging
to the two relations.a new resultant scheme is created consisting of
concatination of all possible combination of tuples.
what are different dbms facilities?
how many types of facilities are provided by a dbms?
1)the data definition facility or data definition language(DDL)
2)the data manipulation facility or data manipulation language(DML)
3)the data control facility(DCL)
what is data definition language?
data scheme is specified by a set of definitions which are expressed b a special
language called a DDL.
what is a data directory or data dictionary?
the result of compilation of DDL statements is a set of tables which are stored
in a special file called data dictionary or data directory.
a data directory is a file that contains metadata i.e data about data.this file
is consulted before actual is read or modified in the database system.