2 Flashcards
used by various users for various purposes
DBMS
can be seen as single tier or multi tier or n-tier architecture
DBMS Architecture
It does not provide handy tools for end users and preferably database designer and programmers use single tier architecture
DBMS/1 Tier Architecture
must have some application, which uses the DBMS
2-tier Architecture
separates it tier from each other on basis of users
3-tier architecture
tells how the logical structure of a database is modeled
Data Model
are fundamental entities to introduce abstraction in DBMS
Data Model
define how data is connected to each other and how it will be processed and stored inside the system
Data Model
Goal– make sure all data objects required by a database are completely and accurately represented
Data Modeling
precise description of the data content in a system
Data Model
Design the database at physical, logical and view level
Data Model
represents the nature of data, and the business logic to control the data. It is also organize the database
Data Modeling
helps to communicate between business people, who requires the computer system, and the technical people who can fulfill their requirements.
Data Modeling
a class of real world objects having common attributes (e.g., sites, variables, methods).
Entity
A characteristic or property of an entity (site name, latitude, longitude)
Attribute
An association between two or more entities
Relationship
the number of entities on either end of a relationship (one-to-one, one-to- many, many-to-many, etc.)
Cardinality
based on the notion of real world entities and relationship among them
Entity-Relationship model
in ER model is real world entity, which has some properties called attributes. Every attribute is defined by its set of values called domain
Entity
The logical association among entities is called. are mapped with entities in various ways. Mapping cardinalities define the number of association between two entities.
Relationship
represented by means of rectangles. Rectangles are named with the entity set they represent.
Entities
the properties of entities. are represented by means of ellipses. Every ellipse represents one attribute and is directly connected to its entity (rectangle).
Attributes
represented by ellipses that are connected with an ellipse
Composite Attributes
attributes are depicted by dashed ellipse
Derived
attributes are depicted by double ellipse.
Multivalued
atomic values, which cannot be divided further. For example, a student’s phone number is an atomic value of 10 digits
Simple attribute
are made of more than one simple attribute.
Composite attribute
the attributes that do not exist in the physical database, but their values are derived from other attributes present in the database.
Derived attribute
-value attributes contain single value.
Single-value attribute
Multi-value attributes may contain more than one values
Multi-value attribute
A set of attributes (one or more) that collectively identifies an entity in an entity set.
Super Key
A minimal super key is called a candidate key. An entity set may have more than one candidate key
Candidate Key
is one of the candidate keys chosen by the database designer to uniquely identify the entity set.
Primary Key
group of single or multiple keys which identifies rows in a table. A Super key may have additional attributes that are not needed for unique identification
Super Key
is a set of attributes that uniquely identify tuples in a table
Candidate Key
super key with no repeated attributes
Candidate Key
column or group of columns in a table that uniquely identify every row in that table
Primary Key
