E-R Diagram with a Ternary Relationship (title Clevel employee-name street branch-citu branch-name employee-10 assets citi emplovee work-on branch 标 Database System Concepts 2.16 @Silberschatz, Korth and Sudarshan
Database System Concepts 2.16 ©Silberschatz, Korth and Sudarshan E-R Diagram with a Ternary Relationship 返回
E-R Diagrams customer-name) (customer-street oan-numbeT amount customer-id customer-city customer loan Rectangles represent entity sets Diamonds represent relationship sets Lines link attributes to entity sets and entity sets to relationship sets Ellipses represent attributes Double ellipses represent multivalued attributes Dashed ellipses denote derived attributes Underline indicates primary key attributes Database System Concepts 2.17 @Silberschatz, Korth and Sudarshan
Database System Concepts 2.17 ©Silberschatz, Korth and Sudarshan E-R Diagrams Rectangles represent entity sets. Diamonds represent relationship sets. Lines link attributes to entity sets and entity sets to relationship sets. Ellipses represent attributes Double ellipses represent multivalued attributes. Dashed ellipses denote derived attributes. Underline indicates primary key attributes
Y E-R Diagram With Composite, Multivalued, and Derived Attributes street-name middle-initia street-number apartment-number fr rst-name last-name street city address state customer-id customer Zip-code hone-number date-of-birth age Database System Concepts 2.18 OSilberschatz. Korth and Sudarshan
Database System Concepts 2.18 ©Silberschatz, Korth and Sudarshan E-R Diagram With Composite, Multivalued, and Derived Attributes
Relationship Sets with Attributes access-date customer-name)(customer-street account-number balance customer-id customer-cIty customer depositor account 标 Database System Concepts 2.19 @Silberschatz, Korth and Sudarshan
Database System Concepts 2.19 ©Silberschatz, Korth and Sudarshan Relationship Sets with Attributes
Roles Entity sets of a relationship need not be distinct The labels "manager"and"worker"are called roles; they specify how em ployee entities interact via the works-for relationship set. Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles Role labels are optional, and are used to clarify semantics of the relationship employee-name employee-ld telephone-number manage] emplovee Tworks-for worker Database System Concepts 2.20 OSilberschatz. Korth and Sudarshan
Database System Concepts 2.20 ©Silberschatz, Korth and Sudarshan Roles Entity sets of a relationship need not be distinct The labels “manager” and “worker” are called roles; they specify how employee entities interact via the works-for relationship set. Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles. Role labels are optional, and are used to clarify semantics of the relationship