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ER Diagrams 2

Roles are indicated in E R diagram by labeling the line that connects diamonds to rectangle. The following figure shows the role indicators MANAGER and the WORKER between the employee entity set and the works for relationship set .



A weak entity set is indicated in the E R diagram by doubly outlined box . In the following figure the weak entity set TANSACTION is dependant on the strong entity set ACCOUNT via the relationship set ACC-TRAN



Non binary relationship sets can also be represented in ER diagram .Consider the entity set CUSTOMER , ACCOUNT & BRANCH through the relationship CAB.


The figure specifies a CUSTOMER may have several account each located in a specific branch of a bank and that an ACCOUNT may belong to several different CUSTOMERS.

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