DA0-002 Data Acquisition and Preparation Practice Question
A data analyst is integrating customer data from two source systems: a CRM and a billing system. The CRM uses a customer ID format of 'CUST-12345', while the billing system uses '12345'. The analyst needs to join records on customer ID. Which two steps are necessary to prepare the data for a successful join? (Choose two.)
⚠ Common exam trap
The trap here is assuming that a simple CAST or CONVERT is enough, but the format difference ('CUST-' prefix) must also be resolved before the join can succeed.
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
✓
Extract the numeric portion from the CRM customer ID to match the billing system format.
The necessary steps are to extract the numeric portion from the CRM ID and to ensure both ID fields share a consistent data type. These actions standardize the join key, allowing records to match correctly across the two systems. Without them, the join would fail due to format and type mismatches, leading to incomplete or incorrect integration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Extract the numeric portion from the CRM customer ID to match the billing system format.
Why this is correct
Extracting the numeric portion from the CRM ID removes the 'CUST-' prefix, making it compatible with the billing system's numeric ID. This is essential for a direct join on the ID fields. Without this step, the join would fail because the formats differ. It standardizes the key across both sources.
- ✗
Apply a hash function to both customer ID fields to anonymize them.
Why it's wrong here
Hashing is used for anonymization, but it would produce different hash values for 'CUST-12345' and '12345' unless the inputs are first standardized. Hashing does not resolve the format mismatch and would actually prevent a successful join. It is not a necessary step for integration; it is a privacy technique.
- ✓
Convert both customer ID fields to a consistent string data type.
Why this is correct
Ensuring both fields are the same data type (e.g., string) prevents join failures due to type mismatches. Even after extracting the numeric part, one field might be integer and the other string. Casting both to a common type guarantees the join condition can be evaluated correctly. This is a fundamental data preparation step for integration.
- ✗
Sort both datasets by customer ID before joining.
Why it's wrong here
Sorting is not required for a join operation in most database systems, which use hash joins or merge joins that handle unsorted data. While sorting can sometimes improve performance for merge joins, it is not a necessary preparation step for correctness. The join will work regardless of order, provided the keys match. Sorting alone does not resolve the format difference.
- ✗
Create a cross-reference table mapping CRM IDs to billing IDs.
Why it's wrong here
A cross-reference table could be used if there were no deterministic relationship between the IDs, but here the numeric portion is the same. Creating such a table would be redundant and require manual effort. The relationship is clear, so a direct transformation is more efficient. This step is unnecessary and adds complexity.
About these practice questions
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JA
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.