Question at position 11 Which statement best describes an Entity–Relationship (ER) data structure?It is made up of tables linked using keys, with data joined together when needed by the systemIt represents information purely as documents with no explicit structureIt stores all data in a single flat file with no relationships between recordsIt uses nodes and edges to represent everything as a graph that can be walkedClear my selection

Question

BlackTom AI · Accepted Answer

An ER (Entity–Relationship) model represents real-world objects (entities), their properties (attributes), and how they relate (relationships); when implemented in a database this maps to tables, columns, and keys. Key knowledge points: an entity becomes a table, an attribute becomes a column, entities are identified by primary keys, and relationships are implemented via foreign keys. Relational databases use joins to combine related tables at query time.

Step-by-step reasoning:
1. Entities and attributes: In an ER diagram you draw entities (e.g., Customer, Order) and list attributes (CustomerID, Name, OrderID, Date).
2. Keys: Each entity has a primary key (Customer.CustomerID, Order.OrderID) to uniquely identify rows.
3. Relationships: A relationship such as “Customer places Order” is implemented by adding a foreign key (Order.CustomerID) that references Customer.CustomerID.
4. Data access: To fetch a customer’s orders the system performs a join between the Customer and Order tables on the key fields; this demonstrates “tables linked using keys, with data joined when needed.”

Example intermediate steps: define tables Customer(CustomerID PK, Name), Order(OrderID PK, CustomerID FK, Date); execute SELECT * FROM Customer JOIN Order ON Customer.CustomerID = Order.CustomerID to retrieve linked data.

Why the correct answer is correct: It precisely describes the relational implementation of an ER design—tables linked by keys and joined at query time—matching standard database theory and practice.

Why the other options are incorrect:
- “Represents information purely as documents” describes document-oriented NoSQL stores (e.g., MongoDB), not ER/relational models.
- “Stores all data in a single flat file” contradicts ER’s emphasis on multiple related entities and normalization.
- “Uses nodes and edges to represent everything as a graph” describes graph databases (e.g., Neo4j), not ER relational schemas.

Conclusion: The correct description is “It is made up of tables linked using keys, with data joined together when needed by the system,” which matches the provided answer.

类似问题

Which of the following best illustrates the relationship between entities and attributes?

Question at position 46 The number of entity types that participate in a relationship is called the: degree.identifying characteristic.number.counter.

Question at position 23 The most common types of entities are:strong entities.associative entities.super entities.weak entities.

Which statement about participation constraints is MOST accurate?

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