DBMS CS2
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The document outlines the concepts of Enhanced Entity-Relationship (EER) modeling and its application in relational database design, focusing on participation constraints and the mapping of ER constructs to relational data models. It discusses key attributes, types of keys such as superkeys, candidate keys, and foreign keys, along with their roles in identifying entities uniquely within a database. Additionally, it emphasizes the importance of normalization and relationships between entities in designing efficient databases.
DBMS CS2
- 1. DBDA (Database Design and Applications) CH2 By: Prof. Ganesh Ingle
- 2. Session objective Quick look of previous Session EER Concepts and notations Modelling class hierarchies Tutorial 1: EER modelling Relational model concepts Relational data model constraints Mapping ER Constructs to relations
- 4. How an entity participate in a relationship??? Total: If every entity in E participates in t=atleast one relationship in R Eg. Student elective subjects at least register for a course. Partial: Some entities in E participates in in relationship R Eg. Student and CR relation( not all the students are participated for being CR) Participation constraint
- 5. ER ASSIGNMENT Draw an ER diagram with following constraint Design a database for film There are no actors in this database that have been in no movies. b. There are some actors who have acted in more than ten movies. c. Some actors have done a lead role in multiple movies. d. A movie can have only a maximum of two lead actors. e. Every director has been an actor in some movie. f. No producer has ever been an actor. g. A producer cannot be an actor in some other movie. h. There are movies with more than a dozen actors. i. Some producers have been a director as well. j. Most movies have one director and one producer. k. Some movies have one director but several producers. l. There are some actors who have done a lead role, directed a movie, and produced some movie. m. No movie has a director who also acted in that movie.
- 8. EER features 1)Generalization: Abstracting process of viewing sets of objects as a single general class. Bottom up approach. 2) Specialization: Introducing new characteristics to an existing class of objects to create new class .Top down approach. 3)Aggregation :Compiling information on an object ,thereby abstracting higher level object. Sub class Super class Inheritance and types WRT to DBMS
- 10. Generalization
- 11. ER diagram to set of Table conversion i.e. converting ER model to relational data model . In relational data model we represent real model in to collection of relations. Relation=table Domain??? Tuple/record/row Attribute/column/ Relational model concepts
- 13. Relational data model constraints Knowing all key concepts PRN SName PPNo Lisc-no DOB Fname 201519TW700 DHAYREEKAR SOHAM RAJENDRA J8369854 AQ1254 14/02/1994 Rajendra dhayrikar 201519TW721 SUTAR VISHAL VIVEK B8369859 AW2568 12/02/1994 Vivek sutar 201437tp101 Karneet singh H9369860 PQR1245 10/02/1994 Jaspreet singh 201537tp145 Sheetal Anil Bhokare Patil M9369950 ABC143 18/12/1987 Anil Bhokare Patil
- 14. A key allows to identify a set of attributes to distinguish entities from each other. Key attribute set KAS Key attribute KA Types of key: Superkey: Set of one or more attributes that allows to identify an entity uniquely.(It may contain extra attributes)eg. {Std_Id,Std_Name,Mobile_no,EmailId} Candidate key: It is minimal set of super key which can uniquely identify an entity. eg. {Std_Id} not id and name both. New definition: SK for which no subset is a superkey. Relational data model constraints Key in Relation
- 15. Relational data model constraints Key in Relation Note : More than one CK is possible in relation Suppose we have 5 CK Primary key: vvimp Chosen by DBA very important to identify the entity and the record. Eg.??? Alternate Key/s: CK-PK=AK ,5-1=4 . All 4 can become PK but not chosen by DBA. Secondary Key: Used for data retrieval. Eg.Emp_id(PK) ,Dept(Secondary key) I want to find the employee wrt to dept then Dept is secondary key. Many time in a Group by clause we use Secondary key. Foreign Key: PK of one related to another entity id FK Composite Key: Combination od two or more columns in a table that uniquely identify the tuple/record/row. Eg.CutomerId,OrderID,SalesDetail
- 16. Key in Relation Let R(A B C D) HOW MANY SUPER KEYS ARE POSSIBLE PROVIDED CK=A
- 17. Key in Relation Let R(A B C D) HOW MANY SUPER KEYS ARE POSSIBLE PROVIDED CK1=A,CK2=B
- 18. Key in Relation Let R(A B C D) HOW MANY SUPER KEYS ARE POSSIBLE PROVIDED CK1=A,CK2=B,CK3=C
- 19. Key in Relation Let R(A1.A2,A3,……An) HOW MANY SUPER KEYS ARE POSSIBLE PROVIDED With only CK A1= 2n-1 With only CK A1,A2= 2n- 2n-1 With only CK A1A2,A3A4= 2n-2+2n-2- 2n-4 With only CK A1A2,A2A3=2n-1- 2n-3
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