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    What is an entity-relationship diagram?


    Have a query about en entity relationship diagram? Searching for a method of drawing an ER diagram? Here, you can go through the steps necessary to come up with an ER diagram for any specific case study.

    Draw an entity-relationship diagram for the following situation:
    Many students play many different sports. One person, called the head coach, assumes the role of coaching all these sports. Each of the entities has a number and a name. (Make any assumptions necessary to complete a reasonable diagram. List your assumptions.)
  • #146808
    An Entity Relation diagram is an aid to understand how the information a system produces is related. There are five important steps in this.
    • Entity: It is an object or concept about which you are interested in storing the information. This is represented by rectangles,
    • Action: This shows how two entities share information in the database and are represented by diamond shapes.
    • Attribute.. An attribute is the unique and specific characteristic of the entity and is represented by Ovals.

    • Connecting line:. This is a solid line that connects attributes to show the relationships of entities in the diagram.
    • Cardinality: Cardinality specifies the maximum number of relationships

    drrao
    always confident

  • #146825
    Assumptions for the situation in question

    Every students can choose many sports to play
    Head Coach can coach one sport at a time
    Head coach coaches all the sports

    As there is no provision to draw the diagram, I Hope you can draw the diagram with the assumptions I have mentioned above with the following steps

    Identify Entity - Entity is the object to store information and is represented by rectangle

    Identify Relationships between two entities and describe the relationship between the entities by drawing a diamond and write a brief description about the relation in it.

    Fill Cardinality by finding the number of occurrences of one entity for a single occurrence of the related entity.

    Define Primary keys by finding the attributes that uniquely defines each entity.
    Identify and map the attributes

    Draw and check the Entity Relationship diagram

  • #146861
    An EDR is a viewed diagram of altered object that exists within a system and how they express each other. Peter Chen introduce the entity relationship model in 1976. ER models are generally used to make relational database. There are three basic components in entity relationship ER diagram is entity, attribute and relationship.
    An entity means any object which exists in the system. It can also be place and person. For example a learning institute may include faculty, candidates, fees, courses subjects and any other object. In ER diagram, entities are represented by a rectangle.
    An attribute is an appearance of an entity. It can also be a land or equity. attributes are represented by elliptical shapes.
    Relationship means you can understand with the word it shows relation between two or more things. In ER diagram, relationship just specify and how entites collaborate. Relationships are represented by a diamond shape. Entity is a first thing to identify if there is any entity then there is any attribute which represent by oval shapes then relationship which describe the interaction of entities.

  • #146897
    Entity relationship diagrams, in simple terms are pictorial/graphic depiction of the interactions between the key components in that given system or event. It's a tool in which data is processed to find the ways to setup a relational oriented database. The ER diagram is similar to analyzing a sentence but in as a pictorial breakup. In the ER diagram, the main players or entities are depicted as circle or oval or points, the relationships between the entities are the lines connecting the above shapes, the degree of these relationship are based on the number of entities in each relationship.

    In this scenario
    Many students, Many sports
    One Head Coach to coach all games
    Give names and numbers to the different sports and differnt players

    The main components are
    1.Entity: This is a definable component, person or an object. The entity can be a strong , weak
    entity or an associative entity.This is usually by drawn as a rectangle
    2. Relationship: This is basically how the entities interaction with each other and depicted as diamonds, can be strong or weak
    3.Attribute. This is a key feature that defines the entity depicted as an oval or a circle. It can be simple or a multi-value attribute.
    4. Cardinality: It's the numerical representation of the relationships between entities. It could be one to one or one to many
    Label them clearly, attributes can be many, so list the most important ones


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