# How to Correctly Model Captains and Players in an NHL ER Diagram?

• Comp Sci
• shivajikobardan
In summary, there are several requirements for a simple database for the National Hockey League (NHL) including multiple teams with various information such as name, city, coach, captain, and players. Each player has a unique team, name, position, skill level, and injury records. A team captain is also a player and games are played between two teams with a date and score. It is not recommended to use "ISA" or generalization for captain and player as they should be considered as separate entities.
shivajikobardan
Homework Statement
My main confusion is can I use "ISA" in captain and player? Can I use generalization there?
Relevant Equations
None
Suppose you are given the following requirements for a simple database for the National Hockey League (NHL):
1) the NHL has many teams,

2) each team has a name, a city, a coach, a captain, and a set of players.

3) each player belongs to only one team,

4) each player has a name, a position (such as left wing or goalie), a skill level, and a set of injury records,

5) a team captain is also a player,

6) a game is played between two teams (referred to as host_team and guest_team) and has a date (such as May 11th, 1999) and a score (such as 4 to 2).
Here's my solution. Is it correct?

My main confusion is can I use "ISA" in captain and player? Can I use generalization there?Here's the solution to this problem.
https://www2.cs.sfu.ca/CourseCentral/354/louie/Chap2_practice_key.pdf

Don't you usually do a functional dependency diagram?

WWGD said:
Don't you usually do a functional dependency diagram?
Not when the question asks for an entity relationship diagram (see the title)
shivajikobardan said:
Homework Statement:: My main confusion is can I use "ISA" in captain and player? Can I use generalization there?
No, your main confusion is that you have two different entities for "captain" and "player".

pbuk said:
No, your main confusion is that you have two different entities for "captain" and "player".
Hmm, so that's a mistake in your opinion?

## What is an ER diagram in DBMS?

An ER (Entity-Relationship) diagram is a visual representation of the relationships between entities in a database management system (DBMS). It uses symbols and lines to depict the entities, attributes, and relationships between them.

## What is the purpose of an ER diagram in DBMS?

The main purpose of an ER diagram is to provide a clear and organized representation of the data and its relationships within a database. It helps in understanding the data model and designing the database structure.

## What are the common symbols used in an ER diagram?

The common symbols used in an ER diagram include rectangles for entities, diamonds for relationships, and ovals for attributes. Other symbols may also be used to represent specific types of relationships or attributes.

## What is the difference between a weak and strong entity in an ER diagram?

A strong entity is an entity that can exist independently and has its own unique identifier. A weak entity, on the other hand, cannot exist without a strong entity and relies on the strong entity for its existence. It is represented by a double rectangle in an ER diagram.

## How do you read an ER diagram?

To read an ER diagram, start by identifying the entities, their attributes, and the relationships between them. Then, look for cardinality and participation constraints to understand the nature of the relationships. Finally, analyze the diagram to understand the data model and the connections between entities.