2.7- Mapping Constraints In ER Diagram In DBMS | Mapping Cardinality Or Cardinality Ratios In DBMS скачать в хорошем качестве

2.7- Mapping Constraints In ER Diagram In DBMS | Mapping Cardinality Or Cardinality Ratios In DBMS

2.7- Mapping Constraints In ER Diagram In DBMS | Mapping Cardinality Or Cardinality Ratios In DBMS Please Follow Playlist For Complete Chapter - Link Is Under Description entity in dbms, erd database, er database, relational database model diagram, er diagram in database management system, PLAYLIST: DBMS - Data Base Management System Tutorials In Hindi | GATE- NET- DBMS Lectures in Hindi    • DBMS Complete Syllabus- All University exa...   dbms tutorials, dbms tutorials in hindi, dbms lectures, gate dbms lectures, ugc net dbms lectures, gate dbms tutorials in hindi, ugc net dbms tutorials in hindi, gate dbms tutorials, ugc net dbms tutorials, #gatedbmslecturesinhindi, #ugcnetdbmslecturesinhindi, #gatedbmslectures, #ugcnetdbmslectures, There are certain constraints in E-R model. Data in the database must follow the constraints. Constraints act as rules to which the contents of database must conform. There are two types of mapping constraints : (a) Mapping cardinalities, (b) Participation constraints. 2.5.1 Mapping Cardinalities (Cardinality Ratios) It specifies the number of entities of an entity set that are associated with entities of another entity set through a relationship set. Mapping Cardinalities are helpful in describing binary relationship sets. Two entity sets X and Y having binary relationship set R must have one of the following mapping cardinality : 1. One to One (1 : 1) : An entity in X is associated with at most one entity in Y and an entity in Y is associated with at most one entity in X. E-R and EER Models 49 A country has only one president. Any person may be the president of at most one country. 2. One to Many (1 : N) : An entity in X is associated with any number of entities in Y. An entity in Y is associated with at most one entity in X. A manager has many employees under it but an employee works under only one manager. 3. Many to One (N : 1) : An entity in X is associated with at most one entity in Y. An entity in Y is associated with any number of entities in X. A employee can work on single project while any project can be assigned to more than one employee. 4. Many to Many (M : N) : An entity in X is associated with any number (zero or more) of entities in Y and vice versa. X (Student) Y (Subject) X1 X2 Y1 Y2 Notes Link: http://www.tutorialsspace.com/Downloa...