The answer is that the cause of this database unique constraint violation error is the attempt to insert a duplicate email address, 'john.doe@example.com', which already exists in the table. This error occurs because the UNIQUE constraint on the 'email' column enforces data integrity by rejecting any INSERT or UPDATE operation that would create a duplicate value, ensuring every row has a distinct identifier for that column. On the Certified Information Systems Auditor CISA exam, this scenario tests your understanding of database controls and how integrity constraints prevent data anomalies—a common trap is confusing UNIQUE constraints with PRIMARY KEY constraints, though both prevent duplicates, UNIQUE allows a single NULL value while PRIMARY KEY does not. To remember this, think of the mnemonic “UNIQUE keeps emails one-of-a-kind,” reinforcing that the database will always reject a second identical entry to maintain referential and entity integrity.
CISA Practice Question: Information Systems Acquisition, Development and Implementation
This CISA practice question tests your understanding of information systems acquisition, development and implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
ERROR: ORA-00001: unique constraint (HR.EMP_EMAIL_UK) violated
INSERT INTO employees (employee_id, email) VALUES (101, 'john.doe@example.com');
Refer to the exhibit. A developer is inserting a new employee record. What is the cause of this error?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The email 'john.doe@example.com' already exists in the table
The error message indicates a violation of a UNIQUE constraint on the 'email' column. The INSERT statement attempts to add 'john.doe@example.com', but that value already exists in the table. The database rejects the operation because the constraint ensures no duplicate email addresses are allowed.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The column 'email' does not exist
Why it's wrong here
The error mentions constraint name.
✓
The email 'john.doe@example.com' already exists in the table
Why this is correct
Unique constraint violation.
Related concept
Read the scenario before looking for a memorised answer.
✗
The table is full
Why it's wrong here
Not indicated.
✗
The employee_id 101 already exists
Why it's wrong here
The constraint is on email, not ID.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may misread the error message and assume it refers to a primary key violation (employee_id) rather than recognizing the specific wording of a UNIQUE constraint violation on the email column.
Detailed technical explanation
How to think about this question
Under the hood, the database uses a unique index on the 'email' column to enforce the UNIQUE constraint. When an INSERT is attempted, the database engine checks the index for an existing entry with the same value; if found, it raises an integrity constraint violation (ORA-00001 in Oracle, SQLSTATE 23505 in PostgreSQL, or similar). In real-world scenarios, this prevents duplicate user accounts or contact records, ensuring data consistency.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CISA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Information Systems Acquisition, Development and Implementation — This question tests Information Systems Acquisition, Development and Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The email 'john.doe@example.com' already exists in the table — The error message indicates a violation of a UNIQUE constraint on the 'email' column. The INSERT statement attempts to add 'john.doe@example.com', but that value already exists in the table. The database rejects the operation because the constraint ensures no duplicate email addresses are allowed.
What should I do if I get this CISA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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