Below is an entity-relationship diagram for a relational database: Which best describes the relationship between customers and sales?

Question

BlackTom AI · Accepted Answer

The diagram shows a one-to-many relationship from tblCustomers to tblSales: the CustomerID in tblCustomers is a primary key (unique, marked with the key icon) and CustomerID appears in tblSales as a foreign key. The relationship line has a "1" at the customer side and an infinity (∞) at the sales side, which explicitly indicates cardinality 1-to-many.

Step-by-step reasoning:
1. Identify keys: tblCustomers lists CustomerID as the primary key; tblSales lists SalesID as the primary key and also contains a CustomerID field.
2. Interpret the foreign key: CustomerID in tblSales refers to the primary key in tblCustomers, so each sales record is associated with exactly one customer (one CustomerID value).
3. Interpret cardinality symbols: The "1" by tblCustomers and the "∞" by tblSales mean one customer may be referenced by many sales rows.
4. Conclude relationship: Because many sales records can hold the same CustomerID but each sale row holds only one CustomerID, a single customer can make many sales (one-to-many).

Why the correct answer is correct:
- The schema and cardinality symbols directly state that one customer can be linked to multiple sales entries. This is the textbook definition of a one-to-many relationship in a relational database.

Why other options are incorrect:
- (a) “One sale can belong to many customers.” Incorrect: tblSales has a single CustomerID field, so each sale points to one customer, not many.
- (b) “A customer can buy other customers.” Nonsensical for this schema—there is no attribute or relationship describing customers buying customers.
- (c) “A customer can only make one sale.” Incorrect: the ∞ at the sales side indicates multiple sales per customer are allowed.

Final confirmation: The correct answer is d. A customer can make many sales.

Below is an entity-relationship diagram for a relational database: Which best describes the relationship between customers and sales?Single choice

Similar Questions

Total participation (or mandatory participation) of an entity in a relationship is indicated by:

In which project stage is an entity-relationship (ER) diagram created?

The above ER diagram means that an employee can work for multiple departments, and a department can have at most one employee.

Question at position 28 In the figure below, what is depicted? A one-to-many relationshipA unary relationshipA one-to-one relationshipAn associative entity

Question at position 2 The lines on a ER diagram represent the entities and should be labeled with nouns just like a DFD diagram.TrueFalse

A one-to-many relationship between two entities is symbolized in a diagram by a line that ends with:

A derived attribute is indicated in the Chen notation by a _____ that connects the attribute and an entity.

In an ER diagram, the weak entity is typically depicted with a ___ _, and the relationship between the weak entity and the strong entity is shown with a _____.

More Practical Tools for Students Powered by AI Study Helper

Homework AI Solver

Stylized AI Paper Writer

Plagiarism Checker Assistant

Citation AI Academic Writing Tool

In-Class Translation Assistant

AI Note Generator

AI Quiz Answers

Past Exam Questions from University Test Bank

Smart Practice Assistant

Adaptive Practice

Making Your Study Simpler