Questions and Answers
Who is responsible for the physical realization of the database in the DB environment?
Database Administrator (DBA)
Which of the following are disadvantages of file systems? (Select all that apply)
What is the abbreviation for DBMS?
Database Management Systems
Nonprocedural languages are also called declarative languages.
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The Schema DDL enables the DBA to define the schema, while the Subschema DDL allows the application programs to define the parts of the database they require.
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What is the purpose of normalization in database design?
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What is the Degree of a relationship type in a database model?
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In a recursive relationship, the same entity type participates only once.
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____ is a property of an entity or a relationship type.
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Match the Database Anomaly with its description:
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Study Notes
Data Administration and DBMS
- A Data Administrator is responsible for managing data resources in a Database Management System (DBMS).
- A DBA is responsible for the physical realization of the database.
- Business rules in a DBMS are constraints defined in a database.
Components of DBMS Environment
- DBMS: Database Management Systems
- DBTG: Data Base Task Group
- IDS: Integrated Data Store
- IMS: Information Management System
- CODASYL: Conference on Data Systems Languages
- ANSI: American National Standards Institute
- GUAM: Generalized Update Access Method
- DDL: Data Definition Language
- DML: Data Manipulation Language
- OODBMS: Object-Oriented Database Management System
- ORDBMS: Object-Relational Database Management System
Disadvantages of File System
- Data redundancy and inconsistency
- Difficulty in accessing data
- Data isolation
- Atomicity issues
- Concurrent access anomalies
- Security problems
System Catalog
- A repository of information describing the data in a database, also known as metadata.
- Also known as data dictionary or data directory.
Hierarchy of Data Organization
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- BIT: Smallest unit of information
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- BYTES: A collection of 8 bits or 1 character
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- DATA ITEMS: A collection of related characters
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- RECORDS: A collection of related data items
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- FILE: A collection of related records
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- DATABASE: A collection of related files
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- INFORMATION SYSTEMS: A collection of related databases
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- CLOUD COMPUTING: A collection of related information systems
History of DBMS
- 1960s: File-based systems
- Mid-1960s: Hierarchical and network models
- 1970: Relational data model
- 1970s: Prototype RDBMS developed
- 1976: Entity-Relationship (ER) model proposed
- 1979: Commercial RDBMS appear
- 1980s: Commercial relational DBMS products (DB2 and SQL/DS)
- 1987: ISO SQL standard
- 1990s: OODBMS and ORDBMS appear
- 1990s: Data warehousing systems appear
- Mid-1990s: Web-database integration
- 1998: XML
Database Languages
- Data sublanguage:
- Data Definition Language (DDL): used to specify the database schema
- Data Manipulation Language (DML): used to both read and update the database
- 2 Types of DML:
- Procedural: specifies how to retrieve data
- Nonprocedural (Declarative language): specifies what data is needed, not how to retrieve it
Three-Level ANSI-SPARC Architecture
- External level: user's view
- Conceptual level: community view
- Internal level: physical representation of the database on the computer
Data Models and Conceptual Modeling
- A data model is an integrated collection of concepts for describing and manipulating data, relationships between data, and constraints on the data in an organization.
- Components of a data model:
- Structural part: set of rules according to which databases can be constructed
- Manipulative part: defines the types of operation that are allowed on the data
- Integrity constraints: ensures data accuracy
- 3 Categories of Data Models:
- Object-based: uses concepts such as entities, attributes, and relationships
- Record-based: consists of a number of fixed-format records, possibly of differing types
- Physical: describes how data is stored in the computer
Functions of a DBMS
- Data storage, retrieval, and update
- User-accessible catalog
- Transaction support
- Concurrency control services
- Recovery services
- Authorization services
- Support for data communication
- Integrity services
- Services to promote data independence
- Utility services
The Information Systems Lifecycle
- Data is one of the most important resources of an organization
- 2 major sources of data:
- Internal data
- External data
Database Design Phase
- Conceptual database design: constructs a database model of the data used in the organization independent of physical considerations.
Entity-Relationship Modeling
- ER modeling is a top-down approach to database design that begins by identifying the important data called entities and relationships between the data that must be represented in the model.
- Entity types: a group of objects with the same properties, which are identified by the enterprise as having an independent existence.
- Entity occurrence: a uniquely identifiable object of an entity type.
- Relationship types: a set of meaningful associations among entity types.
- Relationship occurrence: a uniquely identifiable association that includes one occurrence from each participating entity type.
Attributes and Domains
- Attribute: a property of an entity or a relationship type.
- Attribute domain: the set of allowable values for one or more attributes.
Diagram Symbols and Notations
- Rectangle: strong entity
- Double rectangle: weak entity
- Oval: attribute
- Double oval: multi-valued attribute
- Broken oval: derived/computed attribute
- Rhombus: strong relationship
- Double rhombus: weak relationship
- Lines: connect entities
Functional Dependencies
- Describes the relationship between attributes
- 3 Forms of Database Anomalies:
- Insertion Anomaly
- Deletion Anomaly
- Update Anomaly
Normalization
- A technique for producing a set of relations with desirable properties, given the data requirements of an enterprise.
- Purpose:
- Minimize/reduce data redundancy
- Minimize/reduce the number of attributes/columns
- Prevent DB anomalies
- Simplify DB queries
- History:
- 1970: 1st concept of normalization (1NF)
- 1971: 2NF and 3NF
- 1977: 4NF
- 1979: 5NF
- 1981: DKNF (Domain Key Normal Form)
- 1982: EKNF (Elementary Key Normal Form)
- 2012: ETNF (Essential Tuple Normal Form)
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Description
This quiz covers the basics of Database Management System, including the role of a Database Administrator and the advantages and disadvantages of DBMS.
