What is a disjoint less constraint?
It requires that an entity belongs to no more than one level entity set.
The same entity may belong to more than one level.
The database must contain an unmatched foreign key value.
An entity can be joined with another entity in the same level entity set.
Correct Answer :
A. It requires that an entity belongs to no more than one level entity set.
Disjoint less constraint requires that an entity belongs to no more than one level entity set. (Disjoint less constraint means that an entity can be a member of at most one of the subclasses of the specialization.)
Related Questions
______ keyword is used to find the number of values in a column.
TOTAL
ADD
COUNT
SUM
DBMS helps achieve
Centralized control of data
Data independence
Both A and B
Neither A nor B
If both the functional dependencies : X�Y and Y�X hold for two attributes X and Y then the relationship between X and Y is
M:N
M:1
1:M
The concept of mapping of ______ entity types is the concept in which the for each strong entity type E in the ER schema, create a relation R that includes all the simple attributes of E.
Regular
Irregular
None
Weak
The common column is eliminated in
theta join
outer join
natural join
composed join
What are the desirable properties of a decomposition
Partition constraint.
Dependency preservation.
Redundancy.
Security.
Cascading rollback is avoided in all protocol except
strict two-phase locking protocol.
tree locking protocol
two-phase locking protocol
validation based protocol.
The cost of reading and writing temporary files while evaluating a query can be reduced by
building indices
pipelining
join ordering
none of the above
Use of UNIQUE while defining an attribute of a table in SQL means that the attribute values are
distinct values
cannot have NULL
both (A) & (B)
same as primary key
The set of all values that can be taken by the attribute is called as _______ of the attribute.
Tuple
Cardinality
Degree
Domain
The data models defined by ANSI/SPARC architecture are
Conceptual, physical and internal
Conceptual, view and external
Logical, physical and internal
Logical, physical and view
Which of the following concurrency control schemes is not based on the serializability property?
Two - phase locking
Graph-based locking
Time-stamp based locking
None of these .
Which is the best file organization when data is frequently added or deleted from a file?
Sequential
Direct
Index sequential
None of the above
The size of a data item is called its _______, which can be a field of some record or may be a larger unit such as a record.
Similarity
Granularity
Dimensionality
Arity
Relational Algebra does not have
Selection operator.
Projection operator.
Aggregation operators.
Division operator.
The transactions like adding an employee, enrolling a student in a course are examples of _______
Logical
Physical
None
Theoretical
The ______ language consists of SQL statements for operating on the data (insert, Modify, Delete) in tables that already exist.
Data Manipulation
Data Definition
Data Control
None
A list consists of last names, first names, addresses and pin codes. If all people in the list have the same last name and same pin code a useful key would be
the pin code
the last name
the compound key first name and last name
Tr from next page
DFD stands for
Data Flow Document
Data File Diagram
Data Flow Diagram
Non of the above
Whenever two independent one-to-many relationships are mixed in the same relation, a __________ arises.
Functional dependency
Multi-valued dependency
Transitive dependency
Partial dependency
A transaction is in state after the final statement has been executed.
partially committed
active
committed
none of the above
A data type or format is specified for each _________
Relation
Tuple
Database
Domain
Tree structures are used to store data in
Network model.
Relational model.
Hierarchical model.
File based system.
The default level of consistency in SQL is
repeatable read
read committed
read uncommitted
serializable
The graphical representation of a query is .
B-Tree
graph
Query Tree
directed graph
Which of the following is not a consequence of concurrent operations?
Lost update problem.
Update anomaly.
Unrepeatable read.
Dirty read.
A ____ key specifies a uniqueness constraint that no two distinct tuples in any state r of relation R can have the same value for super key.
Sub
Parent
Candidate
Super
SQL server stores index information in the _____system table
system indexes
syst indexes
sys indexes
sysind
Which of the following constitutes a basic set of operations for manipulating relational data?
Predicate calculus
Relational calculus
Relational algebra
SQL
Change Staff table by removing default of Assistant for position column
ALTER TABLE Staff ALTER position DROP DEFAULT;
ALTER TABLE Staff ALTER position DEFAULT;
ALTER TABLE Staff ALTER DROP DEFAULT;
MODIFY Staff ALTER position DROP DEFAULT;