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
