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Database systems and database management
Types of databases:
- Hierarchical
- Mesh
- Object-oriented
- Relational
DBMS / Database Management System -
A suite of programs used to manage large sets of structured data with ad hoc query capabilities for many types of users
Database:
A collection of data stored in a meaningful way that enables multiple users and applications to access, view and modify data as needed.
Database terms/jargon -
- Record: Collecion of related data items
- File: Collection of record of the same type
- Database: Cross-referenced collection of files
- DBMS: Manages and controls the database
- Base relation: A table stored in a database
- Tuple: A row in a database
- Attribute: A column in a database
- Primary key: Columns that make each row unique
- View: Virtual relation defined by the database to control subjects from viewing certain data
- Foreign key: Attribute of one table that is the primary key of another table
- Cell: Intersection of a row and column
- Schema: Holds data that describes a database
- Data dictionary: Central repository of data element and their relationships.
- Cardinality: The number of rows in the relation.
- Degree: The number of columns in the relation.
- Domain: Is a set of allowable values that an attribute can take.
Database models:
Relational data model -
Uses attributes (columns) and tuples (rows) to contain and organize information.
A primary key is a field that links all the data within a record to a corresponding value.
Hierarchical data model -
Combines records and fields that are related in a logical tree structure.
Can have one child, many children, no children.
Are useful for mapping one-to-many relationships.
Distributed data model -
Has data stored in more than one database, but it is logically connected.
Enable different databases to be managed by different administrators, although one person or group must manage the entire logical database.
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