Entity Relationship Modeling Examples - Learning MySQL [Book]
Entity Relationship Modeling Examples Earlier in this chapter, we showed you how to design a database and understand an Entity Relationship (ER) diagram. It ignores the requirements of many music genres, making it most useful for. Entity Relationship(ER) Model - ER-Diagram is a pictorial representation of data that Any object, such as entities, attributes of an entity, sets of relationship and One-to-many: When more than one instance of an entity is related and linked. ER Entity relationship diagram of a Primary School Contact + One student can be thought by many teacher and vice‐versa is also acceptable.
If you wanted to use the music database in practice, then you might consider adding the following features: Support for compilations or various-artists albums, where each track may be by a different artist and may then have its own associated album-like details such as a recording date and time.
Under this model, the album would be a strong entity, with many-to-many relationships between artists and albums. Playlists, a user-controlled collection of tracks. For example, you might create a playlist of your favorite tracks from an artist. Track ratings, to record your opinion on how good a track is. Source details, such as when you bought an album, what media it came on, how much you paid, and so on. Album details, such as when and where it was recorded, the producer and label, the band members or sidemen who played on the album, and even its artwork.
Smarter track management, such as modeling that allows the same track to appear on many albums.
Entity Relationship Diagram - Data Modeling - UML Diagramming Software
The University Database The university database stores details about university students, courses, the semester a student took a particular course and his mark and grade if he completed itand what degree program each student is enrolled in. We explain the requirements next and discuss their shortcomings at the end of this section. Consider the following requirements list: The university offers one or more programs. A program is made up of one or more courses.
A student must enroll in a program. A student takes the courses that are part of her program. A program has a name, a program identifier, the total credit points required to graduate, and the year it commenced. A course has a name, a course identifier, a credit point value, and the year it commenced.
Students have one or more given names, a surname, a student identifier, a date of birth, and the year they first enrolled. When he finishes the course, a grade such as A or B and a mark such as 60 percent are recorded. Each course in a program is sequenced into a year for example, year 1 and a semester for example, semester 1.Entity Relationship Diagram(ERD) with Example in Hindi [PART 1]
Although it is compact, the diagram uses some advanced features, including relationships that have attributes and two many-to-many relationships. The ER diagram of the university database In our design: Each student must be enrolled in a program, so the Student entity participates totally in the many-to-one EnrollsIn relationship with Program. A program can exist without having any enrolled students, so it participates partially in this relationship.
As a weak entity, Course participates totally in the many-to-one identifying relationship with its owning Program. This relationship has Year and Semester attributes that identify its sequence position.
School Management System ( Entity Relationship Diagram)
Student and Course are related through the many-to-many Attempts relationships; a course can exist without a student, and a student can be enrolled without attempting any courses, so the participation is not total. When a student attempts a course, there are attributes to capture the Year and Semester, and the Mark and Grade. For a real university, many more aspects would need to be captured by the database.
The airline has one or more airplanes. An airplane has a model number, a unique registration number, and the capacity to take one or more passengers. An airplane flight has a unique flight number, a departure airport, a destination airport, a departure date and time, and an arrival date and time. Each flight is carried out by a single airplane. A passenger has given names, a surname, and a unique email address.
A passenger can book a seat on a flight. The ER diagram of the flight database An Airplane is uniquely identified by its RegistrationNumber, so we use this as the primary key. A Flight is uniquely identified by its FlightNumber, so we use the flight number as the primary key. The departure and destination airports are captured in the From and To attributes, and we have separate attributes for the departure and arrival date and time.
ER modeling is an important technique for any database designer to master and forms the basis of the methodology. It is a group of objects with the same properties that are identified by the enterprise as having an independent existence. The basic concept of the ER model is the entity type that is used to represent a group of 'objects' in the 'real world' with the same properties. An entity type has an independent existence within a database. A uniquely identifiable object of an entity type.
School Management System | Editable Entity Relationship Diagram Template on Creately
Diagrammatic Representation of Entity Types Each entity type is shown as a rectangle labeled with the name of the entity, which is normally a singular noun. What is Relationship Type? A relationship type is a set of associations between one or more participating entity types.
Each relationship type is given a name that describes its function. Here is a diagram showing how relationships are formed in a database. What is a degree of Relationship? The entities occupied in a particular relationship type are referred to as participants in that relationship. The number of participants involved in a relationship type is termed as the degree of that relationship.
In the above-figured example "Branch has staff", there is a relationship between two participating entities. A relationship of degree two is called binary degree relationship. Attributes are the properties of entities that are represented using ellipse shaped figures.
Every elliptical figure represents one attribute and is directly connected to its entity which is represented as a rectangle.