Week 7 Flashcards
Databases
organized collection of logically
related data
Database System (DBS):
A system or software designed to manage a database, and run operations on the data requested by numerous clients
Database management system(DBMS):
is the software that interacts with end users, applications, and the database itself to capture and analyze the data
Logical Database Design
Physical view
Involves how data is stored on and retrieved
from storage media
( Hard disks, magnetic tapes, or CDs)
Logical Database Design
Logical view
Involves how information appears to users and
how it can be organized and retrieved Includes more than one logical view of data,
depending on the user
Logical Database Design
Data model
Determines how data is created, represented,
organized, and maintained
(Data structure, Operations, Integrity rules)
Logical Database Design
Hierarchical model
Relationships between records form a treelike
structure
Logical Database Design
Network model
Similar to the hierarchical model but records
are organized differently
Includes multiple parent and child records
Relational Model
most widely used models today
two-dimensional tables (relations)
allow mapping of information from one table to another
Data dictionary:
Stores definitions Data types for fields, default values
Types of relationships:
One-to-many : a single record links to multiple records
One-to-one: a single record in links to a single record
Many-to-one: Multiple records link to single record
Many-to-many : Multiple records link to multiple records
The data in a DBMS is described at three levels:
the conceptual (or logical)
physical
external
Four main operations of a DBMS
- Creating databases and entering data
- Viewing and sorting data
- Extracting data
- Outputting data
DBMS Languages
Data Definition Language (DDL):
specify the conceptual schema
Data Manipulation Language (DML):
specify database retrievals and updates
DML commands (data sublanguage)
can be embedded in a general-purpose programming language( COBOL, C, C++, or Java)
