Question
How do i draw this ER diagram: Explanation of the ER-diagram: The entity set Person includes all persons registered in the system, with attributes PersonID
How do i draw this ER diagram:
Explanation of the ER-diagram:
The entity set Person includes all persons registered in the system, with attributes PersonID (unique identifier), FirstName, LastName, Address, SSN, and PhoneNumber. The attributes HikerHighestPeak and GuideSpecialization are mutually exclusive and can be null.
The entity set GuideCertification includes all certifications of guides, with attributes CertificationName, IssueDate, Academy, Grade, and foreign key GuideID referencing Guide.
The entity set Company includes all companies that hire guides, with attributes CompanyID (unique identifier), CompanyName, StartDate, and EndDate. The attribute EndDate can be null if the guide is currently employed by the company. The relationship set GuideWorksForCompany relates guides to the companies they work for, with foreign keys GuideID and CompanyID.
The entity set Product includes all products that companies sell, with attributes ProductID, Name, Price, and a discriminator attribute ProductType that can have values 'Destination' or 'Package'. The entity set Destination includes all destinations that can be part of a package, with attributes TrackName, Name, Distance, Elevation, and DifficultyRating. The entity set Package includes all packages that companies sell, with attributes PackageName, DifficultyRating, and foreign key ProductID referencing Product. The relationship set PackageContainsDestination relates packages to the destinations they contain, with foreign keys PackageID and DestinationTrackName.
The entity set Club includes all hiking clubs, with attributes ClubID (unique identifier), ClubName, and EstablishmentDate. The relationship set HikerJoinsClub relates hikers to the clubs they join, with foreign keys PersonID and ClubID.
The entity set Brand includes all brands that have representatives, with attributes BrandID (unique identifier) and BrandName. The entity set Representative includes all brand representatives, with attribute Payment and foreign keys PersonID and BrandID.
The entity set Trip includes all trips that the hiking association organizes, with attributes TripID (unique identifier) and StartDate. The relationship set TripToDestination relates trips to the destinations they visit, with foreign keys TripID and DestinationTrackName. The relationship set TripHasGuide relates trips to the guides that participate in them, with foreign keys TripID and GuideID. The relationship set TripParticipation relates hikers to the trips they participate in, with foreign keys PersonID and TripID. The relationship set GuideRating relates guides to the ratings they receive from hikers, with attributes Rating, Timestamp, and foreign keys GuideID and PersonID.
Note that some of the requirements cannot be strictly implemented in the ER-diagram. For example, the requirement that "each guide works for at least one company" is not reflected in the diagram, since a guide can exist in the system without being associated with any company. Similarly, the requirement that "it is recommended that people have finished certain destinations before pursuing some other destination" is not reflected in the diagram, since there is no explicit relationship between destinations that indicates which ones are prerequisites for others. However, these requirements can still be enforced through
could you tell me the relationships of these entity
Sure! Based on the requirements, here are the relationships between the entities:
A person can be a hiker and/or a guide (1:1 or 1:N relationship).
A guide works for at least one company (N:1 relationship).
A company can have zero to many guides (1:N relationship).
A guide can have zero to many certifications, and a certification belongs to only one guide (1:N relationship).
A product is of either a destination or a package type (1:1 or 1:N relationship).
A destination can have zero to many prerequisite destinations, and a prerequisite destination can be a prerequisite for zero to many destinations (N:M relationship).
A package can contain multiple destinations, and a destination can be contained in zero to many packages (N:M relationship).
A hiker can join zero to many hiking clubs, and a club can have zero to many members (N:M relationship).
A person (either a hiker or a hiking club) can represent zero to many brands, and a brand can have zero to many representatives (N:M relationship).
A trip has at least one destination and is participated in by at least four hikers and one guide (N:M relationship between trips, hikers, and guides).
After a trip, a hiker can rate each guide (N:M relationship between hikers, guides, and trips).
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