data base management system

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  • data base management system

    1. 1. Database Management Entity – Relationship (ER) Diagram Prof. Sridhar Vaithianathan
    2. 2. DATA MODELING A Data Model is a map or diagram that represents entities and their relationships.
    3. 3. Some Definitions  A File/Entity/Table: A group or collection of similar records  A record / Tuple: one piece of data, i.e., one student's information, a recipe, a test question.  Records = rows  A field/Attributes: one category of information, i.e., Name, Address, Semester Grade, Academic topic  (Fields = columns)
    4. 4. ER Diagram - Example
    5. 5. CARDINALITY AND MODALITY
    6. 6. Entity Relationship Diagram - Notation Entitiy Relationship Associated Object Mandatory (Exactly) One Optional (Zero or one) One Mandatory Many Optional Many Optional Mandatory
    7. 7. E – R Diagram Example Basket Ball Game Entities: Home Stadium Team Player Games
    8. 8. ER – Diagram Example – Basket Ball Game HOME STADIUM TEAM PLAYER Has Has GAME Participates Has
    9. 9. Entities, Attributes and Relationship  Strong Entity Vs Weak entity ( EMPLOYEE & DEPENDENT)  Simple Vs Composite Attributes  Single Valued Vs Multi Valued Attributes  Stored Vs Derived Attributes  Identifier Attribute – Primary Key  Composite Identifier  Foreign Key  Sub-Type Vs Super Type Relationship
    10. 10. Database Associations Example HOME STADIUM Stadium Id Stadium Name, Capacity, Location TEAM Team Id Team Name PLAYER Player Id Player Name, Position GAME Team id(1) Team id(2) Date Final Score B A S K E T B A L L G A M E
    11. 11. Relationship Example Instructions One-to-One. TEAM Team Id Team Name, Stadium Id Each team has only one home stadium, and each home stadium has only one team. STADIUM and TEAM Place the primary key from one entity to other entity as a foreign key and vice versa. (i.e. foreign key can be placed at either side of the relationship.) One-to-Many PLAYER Player Id Player Name, Position, Team Id Each player is on only one team, but each team has many players. PLAYER and TEAM Place the primary key from the entity on the one side of the relationship as a foreign key in the table for the entity on the many side of the relationship Many-to-Many PLAYER STATISTICS Team id(1), Team id(2), Date, Player Id Points Each player participates in many games and each game has many players. PLAYER and GAME Create a third entity/table and place the primary keys from each of the original entities together in the third table as a combination primary key DATABASE ASSOCIATIONS …
    12. 12. ER – Diagram : Basket Ball Game HOME STADIUM TEAM GAME STATISTICS PLAYER GAME Has Partici -pates Has Has Has
    13. 13. ERD Development Process  Identify the entities  Determine the attributes for each entity  Select the primary key for each entity  Establish the relationships between the entities  Draw an entity model  Test the relationships and the keys
    14. 14. THANKS THANKS THANKS THANKS THANKS

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