0
Subject Name Code Credit Hours
Database System COMP 219 3
Chapter IV
Subject Name Code Credit Hours
Database System COMP 219 3
Data Models
• A collection of tools for describing
– Data
– Data...
Subject Name Code Credit Hours
Database System COMP 219 3
Data Models
• A collection of Conceptual tools for describing
– ...
Subject Name Code Credit Hours
Database System COMP 219 3
Entity-Relationship data model
• It is a high level conceptual d...
Subject Name Code Credit Hours
Database System COMP 219 3
Entity-Relationship data model
• Entity:
-It is a an object that...
Subject Name Code Credit Hours
Database System COMP 219 3
Entity-Relationship data model
• Entity Set:
- A set of entities...
Subject Name Code Credit Hours
Database System COMP 219 3
• Types of Attributes:
• Simple (or) atomic vs. Composite:
• - A...
Subject Name Code Credit Hours
Database System COMP 219 3
Entity-Relationship data model
• Stored Vs Derived
• - Stored at...
Subject Name Code Credit Hours
Database System COMP 219 3
Entity-Relationship data model
• Relationship:
• - It is an asso...
Subject Name Code Credit Hours
Database System COMP 219 3
• Relationship set:
• - It is a set of relationships of the same...
Subject Name Code Credit Hours
Database System COMP 219 3
• Weak Entity Set:
• - No key attributes.
• Identifying Relation...
Subject Name Code Credit Hours
Database System COMP 219 3
Constraints
• Two of the most important constraints are
• a. Map...
Subject Name Code Credit Hours
Database System COMP 219 3
a. Mapping Cardinalities:
Mapping Cardinalities OR CARDINALITY R...
Subject Name Code Credit Hours
Database System COMP 219 3
• a.i. One-to-many
• An entity in set A is associated with zero ...
Subject Name Code Credit Hours
Database System COMP 219 3
a. Mapping Cardinalities:
 a.i. Many-to-One
 One or more no. o...
Subject Name Code Credit Hours
Database System COMP 219 3
• a.i. Many-to-Many
• One or more no. of entities in set A
is as...
Subject Name Code Credit Hours
Database System COMP 219 3
• The participation of an entity set E in a relationship set R i...
Subject Name Code Credit Hours
Database System COMP 219 3
b. Participation Constraints:
• E.G..
Partial participation Tota...
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Dbms chapter iv

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Transcript of "Dbms chapter iv"

  1. 1. Subject Name Code Credit Hours Database System COMP 219 3 Chapter IV
  2. 2. Subject Name Code Credit Hours Database System COMP 219 3 Data Models • A collection of tools for describing – Data – Data relationships – Data semantics – Data constraints • Relational model • Entity-Relationship data model (mainly for database design) • Object-based data models (Object-oriented and Object-relational) • Semistructured data model (XML) • Other older models: – Network model – Hierarchical model
  3. 3. Subject Name Code Credit Hours Database System COMP 219 3 Data Models • A collection of Conceptual tools for describing – Data – Data relationships – Data semantics – Data constraints • Different data Models • - Relational model - Entity-Relationship data model (Conceptual Model-mainly for database design) - Object-based data models (Object-oriented and Object-relational) - Semi structured data model (XML) • Other older models: – Network model – Hierarchical model A Data model is a set of concepts that can be used to describe the structure of the db.
  4. 4. Subject Name Code Credit Hours Database System COMP 219 3 Entity-Relationship data model • It is a high level conceptual data model that describes the structure of db in terms of entities, relationship among entities & constraints on them.. • Basic Concepts of E-R Model: - Entity - Entity Set - Attributes - Relationship - Relationship set - Identifying Relationship I
  5. 5. Subject Name Code Credit Hours Database System COMP 219 3 Entity-Relationship data model • Entity: -It is a an object that exists in the real world. • Example: - Person, Employee, Car, Home etc.. Object with conceptual Existence - Account, loan, job etc…
  6. 6. Subject Name Code Credit Hours Database System COMP 219 3 Entity-Relationship data model • Entity Set: - A set of entities of the same type. • Attributes: - A set of properties that describe an entity.
  7. 7. Subject Name Code Credit Hours Database System COMP 219 3 • Types of Attributes: • Simple (or) atomic vs. Composite: • - An attribute which cant be sub divided. (Eg.Age) • - An attribute which can be divided into sub parts is called • as composite attribute. e.g.. Address- Apartment no. - Street - Place - City - District Single Valued vs. Multivalued: • -An attribute having only one value (e.g.. Age,eid,sno) • - An attribute having multiple values (e.g.. Deptlocat- A dept can be located in several places) Entity-Relationship data model
  8. 8. Subject Name Code Credit Hours Database System COMP 219 3 Entity-Relationship data model • Stored Vs Derived • - Stored attribute is one that has some value where as derived attribute is a one where its value is derived from sa. • -E.g.. SA-DOB • DA- Age derived from DOB. • Key Attribute: • - An attribute which is used to uniquely identify records. • E.g.. eid, sno, dno
  9. 9. Subject Name Code Credit Hours Database System COMP 219 3 Entity-Relationship data model • Relationship: • - It is an association among several entities. It specifies what type of relationship exists between entities.
  10. 10. Subject Name Code Credit Hours Database System COMP 219 3 • Relationship set: • - It is a set of relationships of the same type. Entity-Relationship data model 1 AA 1000 2 BB 2000 100 FFF 10000 1 AA AC 2 BB AD 100 FFF SD Entity E N TI T Y S E T DEPT. ENTITY TYPERelationship SetEmp.. ENTITY TYPE
  11. 11. Subject Name Code Credit Hours Database System COMP 219 3 • Weak Entity Set: • - No key attributes. • Identifying Relationship: • - The relationship associated with the weak entity type Entity-Relationship data model
  12. 12. Subject Name Code Credit Hours Database System COMP 219 3 Constraints • Two of the most important constraints are • a. Mapping Constraints • b. Participation constraints »Participation constraints Total Participation Partial Participation
  13. 13. Subject Name Code Credit Hours Database System COMP 219 3 a. Mapping Cardinalities: Mapping Cardinalities OR CARDINALITY RATIOS, EXPRESSS THE NUMBER OF ENTITIES TO WHICH ANOTHER ENTITY CAN BE ASSOCIATED VIA A RELATIONSHIPSET. • Several types of Mapping Cardinalities. They are, • a.i. One-to-One • An entity in set A is associated with at most one entity in set B and vice versa. e1 e2 e3 d1 d2 d3 Employee Dept.Works for
  14. 14. Subject Name Code Credit Hours Database System COMP 219 3 • a.i. One-to-many • An entity in set A is associated with zero or more no. of entities in set B and an entity in B is associated with at most one entity in A. a. Mapping Cardinalities: e1 e2 e3 d1 d2 d3 Employee Dept.Works for
  15. 15. Subject Name Code Credit Hours Database System COMP 219 3 a. Mapping Cardinalities:  a.i. Many-to-One  One or more no. of entities in set A is associated with at most one entity in B. An entity in B can be associated with any no. of entities in A. e1 e2 e3 e4 d1 d2 d3 Employee Dept.Works for
  16. 16. Subject Name Code Credit Hours Database System COMP 219 3 • a.i. Many-to-Many • One or more no. of entities in set A is associated with one or more no. of entities in set B. a. Mapping Cardinalities: e1 e2 e3 e4 d1 d2 d3 Employee Dept.Works for
  17. 17. Subject Name Code Credit Hours Database System COMP 219 3 • The participation of an entity set E in a relationship set R is said to be total if every entity in E participates in atleast one relationship in R. b. Participation Constraints: Total Participation Partial Participation: The participation of an entity set E in a relationship set R is said to be partial if only a few of the entities in E participated in relationship in R.
  18. 18. Subject Name Code Credit Hours Database System COMP 219 3 b. Participation Constraints: • E.G.. Partial participation Total participation Employee Dept. Manages
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