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Database Systems

TermDefinition
Data raw facts
Information is the result of processing raw data to revel its meaning
Metadata data about data
database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database.
database is a shared, integrated computer structure that stores a collection of raw facts.
data dependence a data condition in which data representation and manipulation are dependent on the physical data storage characteristics.
data independence A condition in which data access is unaffected by changes in the physical data storage characteristics.
data inconsistency exists when different versions of the same data appear in different places.
data consistency exists when the same versions of data appear.
single-user database A database that supports only one user at a time
multiuser database A database that supports multiple concurrent users.
data redundancy same data stored in different places
data warehouse An integrated, subject-oriented,collection of data that provides support for decision making
data anomalies A data abnormality in which inconsistent changes have been made to a database. For example, an employee moves, but the address change is not corrected in all files in the database. data information not updated.
Components of Database System hardware, software, people, data, procedures
Data model simple representation
entity A person, place, thing, concept, or event for which data can be stored.
attributes a characteristic of an entity
relation connection between two entity
constraints A restriction placed on data. for example " A student's GPA must be between 0.00 and 4.00. Help to ensure data integrity
database design The process that yields the description of the database structure and determines structure and determines the databases components.
table A matrix composed of intersecting rows(entities) and columns( attributes) that represent an entity set in the relational model.
functional dependence
primary key an attribute uniquely identifies
foreign key an attribute whose values match the in another table primary keys
Attribute Required-an example Name
Attribute Optional middle name-because every person may not have a middle name
Attribute Simple cannot be divide ex. s.s number
composite key combine primary keys
data dictionary contains the data definition as well as their characteristics and relationship
weak entity exist because of another entity for example student/parent
Chen model
recursive relationship a relationship found within a single entity. Ex
Created by: cristemelton
 

 



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