Database Design Notations

Database Design Notations and their usage
This is an overview of all the Database Design Notations that you will use when drawing Database Model Diagrams and ER diagrams. All these shapes are available in Creately and you can try out a demo or take a look at some sample database models for more context.

Table object in database design is used to represent 'things' in the real world. real-world objects might be a customer, an inventory item or an invoice. Tables are made of rows.

Table object in database design is used to represent 'things' in the real world. real-world objects might be a customer, an inventory item or an invoice. Tables are made of rows.

In Entity Relationship model, an entity notation is a thing of the real world which can be distinguished from other aspects of the real world. An entity may be a physical object such as a house, an event such as a house sale, or a concept such as a customer transaction.

Weak Entity notation cannot be uniquely identified by its attributes alone. It must use a foreign key in conjunction with its attributes to create a primary key. This notation is represented by a double- outlined rectangle. For ex., consider a database for tracking employees. Dependent persons (Jake and Tom) exist in the employee database because their father (an employee) exists in the Employee table.

A key attribute is the unique characteristic of the entity. For ex. Name and hire date are attributes of the entity Employee.

A multivalued attribute can have more than one value at a time for an attribute. For ex., skills of a surgeon is a multivalued attribute since a surgeon can have more than one skill.

Relationships in Entity Relationship Models show how two entities share information in the database structure.

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