CH 1 Databse concepts Flashcards
what Is a database?
a single large repository of data that is defined once and used simultaneous by many users. e.g many departments.
How is data organized in databases?
- they categorize information into logical groups , which are physically stored in files callled tables.
- a table is an orderly collection of records
- a record is a collection of fields
State the properties of a table
-Values are atomic . this means that a column in a table should hold only one piece of data
- column values are of the same kind.
- each tuple is distinct; there are no duplicate tuples
what is DBMS?
Database Management System.
a software program that controls the organization , storage , management , and retrival of data in a databse. e.g MySql ,PostgreSql
DBMS Functions
- offers data dictionary management
- offers data storage management
- offers data intergrity management
- offers database language and application program interface.
offers security management
what is data ?
Raw facts
field ?
a group of characters with a specific meaning
record?
Logically connected fields that describe a person, place, or thing
File
Collection of related records
File System Critique:
evaluating the strengths and weaknesses of different file systems.
It’s about understanding how well a file system performs in various scenarios, and identifying areas where it can be improved.
state a file system data management critique
- requires extensive programming in third-generation language(3gl)
- time consuming
makes ad hoc queries impossible - leads to islands of information
Data dependece ( file system critique)
-Change in file’s data characteristics requires modification of data access programs
-Must tell program what to do and how
-Makes file systems cumbersome from programming and data management views
Stuctural dependence
-Change in file structure requires modification of related programs
Field Definitions and Naming Conventions
-Flexible record definition anticipates reporting requirements
-Selection of proper field names important
-Attention to length of field names
-Use of unique record identifiers
Data Redudancy
-Different and conflicting versions of same data
-Results of uncontrolled data redundancy
*Data anomalies
-Modification
-Insertion
- Deletion
*Data inconsistency
- Lack of data integrity
state the advantages of of databases over file systems.
-Eliminates inconsistency, data anomalies, data dependency, and structural dependency problems
-Stores data structures, relationships, and access paths
what does a database system Environment consist of?
- People
*end users *support *databse analyst
-Hardware
*Servers *End devices *network *storage
- Software
*DBMS *OS *Programming *Application
-Data
-Procedures
*usage policy *security *data handling *data disposal
Database System Type examples
- single-user vs. Multiuser database
-centralized vs distributed
what is a databse Model?
its collection of logical contructs used to represent data structure and relationships within the database.
-conceptual models . logic nature of data representation
-implementation models . emphasis on how data are represented in the database.
give examples of relationships in conceptual models
- one to many (1:M)
-one to one(1:1)
-many to many
give examples of implementation databse models
-Hierarchial.Logically represented by an upside down tree. each parent can have many children . Each child can have only 1 child.
-netowrk.Each record can have multiple parents.Composed of sets
Each set has owner record and member record
-relational. Perceived by user as a collection of tables for data storage
4 advantages of hierarchical Databse Model
-conceptual simplicity
- databse security & intergrity
-data independence
-efficiency
4 disadvantages of hierarchial database model
- complex implementation
- difficult to mange and lack of standards
-lacks structural independence
applications programming and use complexity
4 advantages of network database model
-conceptual simlicity
-handles more relationship types.
-promotes databse intergrity
-data independence
2 disadvantages of network
system complexity
lack of structural independence
advantages of relational db model
-structural independence
-improved conceptual simplicity
-powerful databse management system.
-Ad hoc query cabability with SQL
- easier database design , implementation , management & use.
disadvantages of relational db model
-poor design and implementation is made easy.
-may promote “islands of information” problems
-substantial hardware and system software overhead
define entity relationship model
Complements the relational data model concepts. based on entities , relationships & attributes. represented in erd diagram.
er db model advantages
-exceptional conceptual simplicity
-visual representation
-effective communication tool
integrated with relational db model
disadv of er db model
loss of information content
no data manipulation language
limited constraint representation
define oo db model
Objects or abstractions of real-world entities are stored . attributes describe properties.
-Collection of similar objects is a class
*Methods represent real world
actions of classes
*Classes are organized in a class
hierarchy
Advantages of oo data model
- adds semantic content.
- database integrity
-both structural and data independence.
-
diadvantages of OO data model
-lack of OODM
-complex navigational data access
-steep learning curve
-high system overhead slows transactions.
state characteristics of database models and the internet.
-Supports complex data types and relationships
-Powerful DBMS GUI make DBA job easier
-Many database design, implementation, and application development tools
-Easily used, developed, and supported
