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Database
collection of interrelated data organized in such a way that it corresponds to the needs and structure of an organization and can be used by more than one person for more than one application
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DBMS
Database management system, enables storage of data in the database, retrieval of data from the database and control of the database
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Data
Raw facts that can be recorded and perserved
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Focuses on the proper generation, storage, and retrieval of data and is a core activity of any organization
Data management
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Difference between information and data
- Data is raw facts that can be recorded and information is the result of the raw data that emphasises a MEANING in a given context
- -Data generates information
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What are some of the issues with file-based systems
- -Data redundancy (same info across multiple files)
- -Isolation of data in separate systems
- -Data inconsistency (lack in data integrity so if you change it in one file it won't apply to other files with the same data)
- -Data Anomalies
- -Program-data dependence
- -Implies "flat" data files / two types of data in one table
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Defining features of a database system
- -Security: collection of programs that manages the database structure and controls access to the data
- -Provides access to the data via a query language
- -Makes data management more efficient and effective
- -Produce quick answers to ad hoc queries
- -Probability of data inconsistency is reduced
- -Promotes integrated view of organization's operations
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Advantages of a database system
- -Minimize data redudancy
- -Data consistency
- -Integration of data
- -Improve data sharing
- -Enforcement of standards
- -Ease of application development
- -Uniform security, privacy, and integrity
- -Data independence from applications
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Components of a database system are
- Hardware
- Software
- People
- Procedures
- Data
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What are some examples of a the software component of database systems
- Microsoft access
- Microsoft SQL
- Oracle
- MySQL
- Systems that are easier but often more limited
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What are some examples of people involved with database systems
- System administrators
- Database administrators (DBAs)
- Database designers
- System analyst and programmers
- End users
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Database classification dealing with determination of single user or multi user databases
Number of users
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Database classification dealing with whether the system is centralized or distributed
Database location
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Database Classification dealing with whether it's operational or data warehouse
Type of use
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Describe a parent - child based database model and it's issues
Hierarchical database model, can be difficult to find data because there's only one way to get there, ex. windows registry
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Describe a parent child based database model where that allows more than one parent
Network database model, tried to solve the problem of hierarchical to access from multiple points
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Updating single publisher's phone number requires you to update multiple entires is an example of
Update anomalies, a problem with flat databases
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Describe the components of a relational database model
- Table- "relation" matrix of intersecting rows
- Entity - which data is collected and stored
- Attributes - characteristics
- Relationships - connections
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You cannot insert information about an author until we have a book by that author is an example of
Insertion anomalies, problem with flat databases
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If we remove a record of a book we loose information about the publisher too is an example of
Deletion anomalies, a problem with flat database
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Set of relations
database
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Row of a relation, with each cell consisting of specific values for a particular variable or attribute
Tuple
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Properties of relations
- Every relation must have a distinct name
- each cell is atomic
- Each attribute in a table must have distinct name
- Values of any attribute must be from the same domain
- There should not be any duplicate tuples
- Order of tuples has no significance
- Order of attributes has no significance
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