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CS 4001 Quiz 1

Terms in this set (47)

The characteristic provided by DBMSs and data models that allows program-data independence and program-operation independence is
data abstraction
A fundamental characteristic of the database approach is that the database system contains not only the database itself but also a definition or description of the database structure and constraints. (T/F)
T
A data model is used to describe the structure of a database. Which of the following concepts are included in the structure/schema of a database?
(a) data types
(b) relationships
(c) constraints
(d) All of the above
(d) All of the above
Which of the following statements is true?
(a) End users of a database must know details about the storage structures used by the database system.
(b) Application programmers are responsible for the physical design of the database.
(c) The database administrator is responsible for authorizing access to the database and for maintaining an adequate database system performance level.
(d) All of the above
(c) The database administrator is responsible for authorizing access to the database and for maintaining an adequate database system performance level.
Which of the following is an example of a representational data model?
(a) entity relationship data model
(b) relational data model
(c) access path model
(d) none of the above
(b) relational data model
The data in the database at a particular point in time is called a ________.
(a) database state
(b) database schema
(c) meta state
(d) logical database
(a) database state
The goal of the three schema database architecture is to separate the user applications from the physical details of a database.
(a) True
(b) False
(a) True
Suppose we change the conceptual schema to add a constraint to the database. The applications and the external schemas for the database do not have to be changed. This is an example of what concept?
(a) program operation independence
(b) physical data independence
(c) logical data independence
(d) procedural independence
(c) logical data independence
Data definition, view definition and data manipulation are handled in one integrated language known as SQL in current database management systems based on the relational data model.
(a) True
(b) False
(a) True
Which of the following is an important aspect of the three schema database architecture?
(a) It allows end-users to directly access the internal schema in their data requests.
(b) It provides the capability for the DBMS to map a data request at a higher level (application oriented) to a request at a lower level (data storage specific) in the 3 schema architecture.
(c) It provides a runtime database processor.
(d) none of the above
(b) It provides the capability for the DBMS to map a data request at a higher level (application oriented) to a request at a lower level (data storage specific) in the 3 schema architecture.
Which of the following is true about a high-level data manipulation language?
(a) It can be embedded in a general purpose programming language.
(b) It can be used as a standalone query language.
(c) It is considered to be procedural since it retrieves records individually.
(d) Both (a) and (b)
(d) Both (a) and (b)
Which of the following is true about the query optimizer component of a DBMS?
(a) It involves reordering of operations for a given query
(b) It involves elimination of redundancies embedded in queries
(c) It involves use of indexes to make queries run faster
(d) All of the above
(d) All of the above
When a defining a database,
specify the data types, structures and constraints of the data to be stored (self-describing nature of a database system; look at the database catalog to glean information about the database structure)
Description of DBMS:
- a collection of programs
- enables users to create and maintain a database
Definition of Meta-Data:
- defines structure of the database
- database definition or descriptive information
- stored by the DBMS in the form of a database catalog or dictionary
Query:
causes some data to be retrieved
Application program:
Accesses database by sending queries to DBMS
Transaction:
May cause some data to be read and some data to be written into the database
Protection includes:
- system protection
- security protection
Phases for designing a database:
- Requirements specification and analysis
- Conceptual design
- Logical design
- Physical design
Database approach (vs. traditional file processing):
Single repository maintains data that is defined once and then accessed by various users
Main characteristics of database approach:
- Self-describing nature of a database system
- Insulation between programs and data, and data abstraction
- Support of multiple views of the data
- Sharing of data and multi-user transaction processing
Program-data independence:
Structure of data files is stored in DBMS catalog separately from access programs
Program-operation independence:
- Interface includes operation name and data types of its arguments
- Implementation can be changed without affecting the interface
Operations specified in two parts:
1) interface and 2) implementation
Data abstraction
Allows program-data independence and program-operation independence
Conceptual representation of data
Does not include details of how data is stored or how operations are implemented
Data model
Type of data abstraction used to provide conceptual representation
Concurrency control software
Ensure that several users trying to update the same data do so in a controlled manner
Controlling redundancy
- Data normalization
- Denormalization: Sometimes necessary to use controlled redundancy to improve the performance of queries
Dynamic aspect or behavior of a database application
Allows the database designer to specify a set of valid operations allowed on database objects
Database schema
Description of a database
Schema construct
Each object in the schema
Database state or snapshot
Data in a database at a particular point in time
The Entity-Relationship model is an example of which type of data model?
(a) physical data model
(b) representational data model
(c) conceptual data model
(d) none of the above
(c) conceptual data model
Degree of a relationship type
Number of participating entity types
(binary, ternary)
Weak identity types are identified by...
being related to specific entities from another entity type
Specialization definition (EER Diagram):
Process of defining a set of subclasses of an entity type
Generalization definition (EER Diagram)
Process of defining a generalized entity type from the given entity types; generalize into a single superclass
Specialization hierarchy vs. Specialization lattice
hierarchy - every subclass participates as a subclass in only ONE class/subclass relationship
lattice - subclass can be a subclass in more than one class/subclass relationship
Multiple inheritance
Subclass with more than one superclass
The Query Optimizer is concerned with...
the rearrangement and possible reordering of operations,elimination of redundancies, and use of correct algorithms and indexes during execution
High-level vs low-level data manipulation language (DML):
A high-level or nonprocedural DML can be used on its own to specify complex database operations concisely.
A low-level or procedural DML must be embedded in a general-purpose programming language
Relational data model
The basic relational data model represents a database as a collection of tables, where each table can be stored as a separate file.
Entity-Relationship (ER) model is a popular high-level conceptual data model
...
Entity set
The collection of all entities of a particular entity type in the data-base at any point in time
Value set (or domain of values)
specifies the set of values that may be assigned to an attribute for each individual entity
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