Chapter 3 database
• users never get direct access to database
the hierarchy of data
• bit: circuit that is either on or off
• byte: typically made up of eight bits
• character: basic building block of information
• field: name, number, or combination of characters that describes an aspect of a business
object or activity
• record: collection of related data fields
• file: collection of related records
• database: collection of integrated and related files
data entities, attributes, and keys
• entity: a general class of people, places, or things (objects) for which data is collected,
stored, and maintained
• attribute: a characteristic of an entity
• key:A field or set of fields in a record that identifies the record
• primary key:Afield or set of fields that uniquely identifies the record.
The relational database model
• manipulating data
◦ selecting: Manipulating data to eliminate rows according to certain criteria.
◦ Projecting: Manipulating data to eliminate columns in a table.
◦ Joining: Manipulating data to combine two or more tables.
◦ Linking: Data manipulation that combines two or more tables using common data
attributes to form a new table with only the unique data attributes.
Data modeling and database characteristics
• when building a database, an organization muse consider
◦ content: what data should be collected and at what cost
◦ access:What data should be provided to which users and when?
◦ Logical structure. How should data be arranged so that it makes sense to a given user?
◦ Physical organization. Where should data be physically located?
• climate-controlled building or set of buildings that: houses database servers and the systems
that deliver mission-critical information and services
• traditional data centers:An approach to data management whereby each distinct operational
system used data files dedicated to that system.
• logical design: abstract model of how data should be structured and arranged to meet an