DATABASE
DATABASE
MGMNT
MGMNT
SYSTEM
SYSTEM
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Database Systems: Understanding Entities, Relational Model, and Hierarchical Model, Study notes of Database Management Systems (DBMS)
An overview of database systems, focusing on entities, attributes, records, and the relational and hierarchical models. It covers the concepts of data independence, metadata, data encoding, data control and protection, and various data models. The text also discusses the advantages and disadvantages of hierarchical and network models.
Typology: Study notes
2010/2011
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DATABASEDATABASE
MGMNT MGMNT
SYSTEM SYSTEM
KEYWORDSKEYWORDS
DATABASE DATABASE
ENTITY ENTITY
RELATIONSHIP RELATIONSHIP
ATTRIBUTES ATTRIBUTES
DATABASE MANAGEMENT SYSTEM DATABASE MANAGEMENT SYSTEM
Cont….Cont….
ENTITIES ATTRIBUTES ANDENTITIES ATTRIBUTES AND
ASSOCIATION ASSOCIATION
ENTITY ENTITY
•A THING OR OBJECT•A THING OR OBJECT
•A DISTINGUISHABLE OBJECT•A DISTINGUISHABLE OBJECT
ABOUT WHICH WE WANT TOABOUT WHICH WE WANT TO
COLLECT INFORMATIONCOLLECT INFORMATION
Cont….Cont….
ATTRIBUTESATTRIBUTES
•PROPERTY OF AN ENTITY•PROPERTY OF AN ENTITY
•INFORMATION THAT WE WANT TO•INFORMATION THAT WE WANT TO
COLLECT ABOUT AN ENTITYCOLLECT ABOUT AN ENTITY
Cont….Cont….
EMPLOYEE ID
EMPLOYEE NAME
EMPLOYEE ID
EMPLOYEE.NAME
EMPLOYEE ID
EMPLOYEE NAME
A) ONE TO ONEONE TO ONE
EMPLOYEE ID EMPLOYEE SALARY SALARY EMPLOYEE ID EMPLOYEE ID SALARY
B) ONE TO MANYONE TO MANY
(MANY TO ONE RLTN BTW EMPLOYEE ID & SALARY)
RELATIONSHIP AMONG ENTITIES RELATIONSHIP EXIST AMONG DIFF ENTITIES EVEN THOUGH RELATIONSHIP MAY INVOLVE MORE THAN TWO ENTITIES - WE WILL CONCENTRATE ON THE RELATIONSHIP BTW TWO ENTITIES
STUDENTS ENROL COURSE LMNT
ENTITY SETS RELATIONSHIP
BORROWER
BORROWER
CUSTOMER LOAN
CUSTOMER LOAN
ONE TO ONE
ONE TO MANY
REPORTS TO
EMPLOYEE
BINARY RELATIONSHIP INVOLVING SAME ENTITY