Why study database management?
- Prevalence
- Advantages over conventional file processing system regarding data independence & the ANSI/SPARC architecture
Why are databases better than conventional file processing?
- Spreadsheets don’t scale well with size
- Difficulty linking tables
- slow to run queries
- incorrect results due to denormalized data
What are other problems with a File System approach?
- complexity in administration
- data integrity/consistency
- data quality for decision making
- program and data dependence
- insufficient backup & recovery mechanisms
- concurrent access
- data security
What are advantages of a database?
- Improved data sharing
- Improved data security
- Better data integration
- Minimized data inconsistency
- Improved data access
- Improved decision making
- Increased end-user productivity
What are the 3 layers of the ANSI/SPARC architecture?
External layer (views) Logical/conceptual layer (tables) Internal/Physical layer (data structure, disk pages)
How does ANSI/SPARC architecture support DBMS characteristics?
- Data independence
- multiple views of the data (security)
What is the physical part of the schema of ANSI/SPARC architecture?
- How data is stored on the disc
- data storage structures
- access paths to the data
What is the logical part of the schema of ANSI/SPARC architecture?
- how we think the data is organized
- conceptual structure
- integrity constraints
What is the external part of the schema of ANSI/SPARC architecture?
- What a user sees of the data
- View is often limited by security
What does data independence mean?
each level is independent in the sense that a complete different organization can be used
Physical data independence
Physical level can change without having to change the logical level
Logical data independence
Logical level can change without having to change the external level
What are the main costs of using a DBMS?
- high initial investment
- may need additional hardware
- overhead
- training
When may a DBMS be unnecessary?
- Application is simple, well-defined and not expected to change
- stringent real time requirements
- Access to data by multiple users is not needed
Data
facts, texts, graphics, sound and video segments that have meaning in the user’s environment
Database
an organized collection of logically related data , designed to meet the information needs of an organization
-designed, built and populated for a specific purpose
What does CRUD stand for?
Creation
Retrieval
Update or modification
Deletion
*For data to be useful , should be able to perform these core operations
DBMS
- Software that supports the creation and maintenance of databases
- Manages the interaction between the end user and the database
Components of a database
- Query language processing
- Report generation
- Security & recovery
- Integrity mgmt
- Data & schema definition
- Concurrency control
- Physical access
Information
data processed to be useful in decision making
Metadata
data that describes the properties or characteristics of other data (e.g. the header of a table)
