DA0-002 Data Concepts and Environments Practice Question
A data analyst is examining a dataset of employee records. The 'EmployeeID' column contains unique alphanumeric codes, and the 'Department' column contains values like 'Sales', 'HR', and 'IT'. The analyst needs to determine which column is a key and which is a categorical attribute. Which statement correctly identifies the data types and roles?
⚠ Common exam trap
The trap here is assuming that any alphanumeric column is categorical, when uniqueness determines whether a column is a key.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
EmployeeID is a key, and Department is a categorical attribute.
EmployeeID uniquely identifies each employee, so it is a key. Department has a limited set of repeated values, so it is a categorical attribute. This distinction is essential for data modeling and analysis. The other options incorrectly assign roles or claim both are keys or both are categorical.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Both EmployeeID and Department are keys.
Why it's wrong here
A key must be unique for each row. Department has multiple employees in the same department, so it cannot serve as a key. Treating Department as a key would cause duplicate key errors and prevent unique identification of records. Only EmployeeID satisfies the uniqueness requirement for a key.
- ✓
EmployeeID is a key, and Department is a categorical attribute.
Why this is correct
EmployeeID uniquely identifies each row, making it a primary key. Department contains a limited set of repeated labels, making it a categorical attribute. This distinction is fundamental for data modeling: keys are used for joining and ensuring uniqueness, while categorical attributes are used for grouping and filtering.
- ✗
Both EmployeeID and Department are categorical attributes.
Why it's wrong here
While Department is categorical, EmployeeID is not a category but a unique identifier. Categorical attributes represent a finite set of labels used for grouping, whereas EmployeeID has high cardinality and is used for identification. Classifying EmployeeID as categorical would ignore its role as a key and could lead to incorrect analysis.
- ✗
EmployeeID is a categorical attribute, and Department is a key.
Why it's wrong here
EmployeeID contains unique codes for each employee, which qualifies it as a key, not a categorical attribute. Department has repeated values and represents categories, so it is not a key. Reversing these roles would lead to incorrect data modeling, such as using Department for joins, which would fail because it is not unique.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This DA0-002 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DA0-002 exam.