Understanding Entity-Relationship Modeling

What is an entity in an Entity-Relationship model?

• An entity is a process that occurs in the system.

• An entity is a distinct object or thing in the real world that can be identified.

• An entity is a collection of attributes that describe a thing.

• An entity is a type of relationship between two objects.

Define a relationship in the context of ER modeling.

• A relationship is a unique identifier for an entity.

• A relationship defines the attributes of an entity.

• A relationship in ER modeling is a type of entity.

• A relationship in ER modeling represents an association between two or more entities.

What is the purpose of an attribute in an ER diagram?

• To represent the relationships between different databases.

• To define the primary key of an entity.

• To store the actual data values in the database.

• To describe properties of entities or relationships in a database.

Explain the difference between a strong entity and a weak entity.

• A strong entity is always a subclass of a weak entity.

• A strong entity has a primary key and can exist independently, while a weak entity depends on a strong entity for its identification and cannot exist on its own.

• A weak entity has a primary key and can exist independently.

• A strong entity cannot have relationships with other entities.

What does a diamond shape represent in an ER diagram?

• An attribute of an entity.

• A primary key in a table.

• A data type for an entity.

• A relationship between entities.

How do you represent a one-to-many relationship in an ER diagram?

• Use a line with a crow's foot notation at the 'many' end to connect the two entities.

• Represent it with a single line without any notation.

• Connect the entities with a solid line at both ends.

• Use a dashed line to connect the two entities.

What is the significance of primary keys in an ER model?

• Primary keys are used to group similar records together.

• Primary keys are essential for uniquely identifying records and ensuring data integrity in an ER model.

• Primary keys are optional and can be omitted in an ER model.

• Primary keys can be duplicated across different tables.

Describe the role of foreign keys in relational databases.

• Foreign keys enforce referential integrity between tables in a relational database.

• Foreign keys are primarily used for data encryption.

• Foreign keys are used to create indexes on tables.

• Foreign keys allow for the duplication of data across tables.

What is normalization, and how does it relate to ER modeling?

• Normalization is a method for increasing data redundancy.

• Normalization is unrelated to data integrity in ER modeling.

• Normalization is the process of organizing data to reduce redundancy and improve integrity, and it relates to ER modeling by structuring entities and relationships effectively.

• Normalization only applies to physical database design.

How can you convert an ER diagram into a relational schema?

• Use UML diagrams to represent the schema.

• Write a narrative description of the database structure.

• Draw a flowchart of the entities and relationships.

• Create tables for entities, define primary keys, establish foreign keys for relationships, and create junction tables for many-to-many relationships.