Db revision
A set of attributes that used to distinct the DB rows which does not contain redundant attributes and to be conisdered for implementation is called? A- super key B- candidate key C -alt key D- all
B
An attribute should not be mapped from ER diagram into a relational schema A-simple attribute B-derived attribute C-composite attribute D-multi vauled attribute
B
Null values in relation is A-an integer value of zero B-unknown or inapplicable data C- empty string D- all
B
One of the follwing is right about table database relation A- the value of foreign key cant be null B- a foreign key may reffernce the relation it belongs to C- a relation schema can have multiple primary keys D- the tuples within a relation must be ordered
B
The degree of a relation is nocisdered as : A the number of tuples B the number of atteibutes C the number of relationshops D none
B
The value of the primary key must not be null this defines A- key B- enitity C- forigen key constraints D-refferntial
B
Which of the following is not property of a relation? A- the value of any attribute must be of the same domain B-all tuples must be ordered C-all of the entries in any attribute must be of the same domain D- no two tuples in a relation may be identical
B
Deleting tuple from relation may violate A-primary key constraints B-entity integrity C-referential integirty D-all
C
Deleting tuples from a relation my be violate A-key constraints B-entity integrity C-referential D- all
C
The primary key Attributes PR of each relation schema cannot have null values in any tuples this defines? A- domain constraints B- key constrantis C-entity integirty constraints D-referential integrity
C
Domain of an attribute can be specified by A- set of values B- name C- data types D- all
D
Null values means? A-existed but unknown at present B-not applicable C-applicable but not assigned yet D - all
D
The domain of an attribute can be specifed by A name B set of value C data types D all of them
D
Which is correct depending on definition of relation A-every relation must have a key B-only single value can be stored in one attribute within tuple C-duplicate tuples are not allowed in a relation D- all
D
Which is the following is an accurate statement? A-every relation must have a key B-only single value can be stores in one attribute within tuple C-duplicate tuples are not allowed in a realtion D- all of above
D
One of the following sttments of a database relation is wrong A- each attribute has a distict name B- values of an attribute comes from the same domain C-ordering of tuples in a relation instance is not important D-each value in a tuples must be atomic single value E-relation instance may have dublicate tuples
E
A domain of an attribute can be specfied by the data type only
False
A foreign key in a relation should always refer to another different relation
False
A foreign key value cannot be null
False
A relation ordering of values whin in a tuple is important
False
Candidate key is a set of attrubutes used to distinct the db rows which may contain redundant attrbiutes
False
Every table is a relation
False
In a relational model, the ordering of values within a tuple is important
False
Only primary keys can be constrained to be not null
False
Ordering of tuples in a relation has no signitificence while ordering of attributes is important
False
Relation instance may have duplicate tuples
False
The foreign key cant refernce the relation it belongs to
False
The value of the primary key must not be null , this defines a primary key constraints
False
The value of the primary key must not be null this defines a primary key constraints
False
A foreign key may reference the relation it belongs to
True
A partial key can uniquely identify the entity that contains it
True
A relation state (instance) of any relation schema is a set of all ots tuples
True
A single relation can have more than one foreign key
True
Cardinality of a relation is the number of tuples in a relation
True
Foreign key may reference the relation it belongs to
True
In a relational model , the number of tuples is represnting the relation degree
True
In the relation model an atomic value in indivisble
True
Referential integnty consttraints used to specify a relationship among tuples in two relation
True
The relation model an atomic value is indivisible
True
