ER Diagram Lecture Notes – It is believed that the ER Diagram can be a powerful tool in data mining. This is because it lets users to see complex relationships in a simple format. The fundamentals are the same wherever you are working. One of the first steps is identifying “what” your system is. A rectangle represents the entity and should have ample space. Incorporate ovals as attributes and connect them with the entity. Leave a little space between the rectangular area and the oval.
Every single entity on the ER diagram is called an attribute. Attributes are property or trait in an organization. In the case in an ER diagram the Inventory Item Name is one of the attributes that belongs to the inventory of an entity Item. The entity can have as many attributes as it needs, and each attribute may have distinct attributes. For instance, a customer’s address can have an address, street number as well as a city and state. These are composite attributes, which means there aren’t restrictions on the number of each.
The next stage in the analysis of an ER diagram would be to establish the amount of information that each entity is able to provide. The cardinality of each company is defined as the number of variables that exist between two entities. A customer, for instance, could buy several phones on the same service on one phone, and the cell phone provider may have several phones under only one bill. The ER diagram can help make it easier to determine the links between the entities. Furthermore, it could aid in determining the type of data that connects each of the entities.
As the system expands and becomes more complicated the ER diagram may become dense and difficult to understand. The complex nature is the reason why an ER diagram demands more precise representation of the micro-level. A well-designed ER diagram can help you understand a system in a greater depth. Just remember to include white space between tables in the ER diagram to ensure that there is no confusion. If you don’t do this, it could be difficult to identify the connection between two different entities.
A person is an individual. An entity is an object or class. An entity can be a person, a city, or an organization. A weaker entity is one that relies on anotherentity, but lacks the essential attributes. An attribute describes a property of an object. The person who is in the ER diagram is a noun. Similarly, the city has a status of an organization. Hence, a connection exists between two entities is a noun.
The attributes that make up the ER diagram should be labeled. A teacher entity could have multiple subject values. Students may have multiple subjects. The relation between two entities is represented by diamond shapes. These lines are typically marked with verbs. Then, they are known as entities. If a pupil is confused regarding the meaning behind an attribute and is unsure of its meaning, the ER diagram can aid in understanding the connection between two different objects.
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