Quick Answer
The correct answer is aggregation with GROUP BY. This is because the task of counting orders per customer requires grouping all rows that share the same customer_id into a single summary row, then applying the COUNT function to tally the number of orders within each group. The GROUP BY clause in SQL is specifically designed for such per-category aggregations, transforming raw transactional data into meaningful summaries. On the CompTIA Data+ DA0-001 exam, this concept frequently appears in scenario-based questions where you must choose the right SQL clause to answer business questions like “how many orders per customer” or “total sales per region.” A common trap is confusing GROUP BY with ORDER BY—remember that ORDER BY only sorts results, while GROUP BY collapses rows into groups for aggregation. A helpful memory tip: “GROUP BY groups, ORDER BY orders—if you need a count or sum per category, GROUP BY is your friend.”
This DA0-001 practice question tests your understanding of comparing and contrasting data concepts. 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.
A company's database has a table 'orders' with columns: order_id, customer_id, order_date, and total_amount. A data analyst needs to identify customers who have placed more than 5 orders in the past year. Which data concept should be used to group orders by customer and count them?
Joining with other tables
Why wrong: Joining combines tables, not needed here.
Filtering with WHERE clause
Why wrong: Filtering selects rows, does not group.
Sorting with ORDER BY
Why wrong: Sorting orders results, does not group.
Aggregation with GROUP BY
GROUP BY groups rows and aggregation functions compute counts.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Aggregation with GROUP BY
Option D is correct because the requirement to count orders per customer requires grouping rows by customer_id and then applying a count function. The GROUP BY clause in SQL aggregates rows that share a common value (customer_id) into summary rows, and the COUNT function tallies the number of orders per group. This is the standard approach for such 'per-customer' aggregations.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Joining with other tables
Why it's wrong here
Joining combines tables, not needed here.
Filtering with WHERE clause
Why it's wrong here
Filtering selects rows, does not group.
Sorting with ORDER BY
Why it's wrong here
Sorting orders results, does not group.
Aggregation with GROUP BY
Why this is correct
GROUP BY groups rows and aggregation functions compute counts.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse filtering (WHERE) with aggregation (GROUP BY), thinking that a WHERE clause alone can count orders per customer, when in fact WHERE only filters rows and cannot produce grouped counts.
Detailed technical explanation
Under the hood, GROUP BY partitions the result set into groups based on the specified column(s), then aggregate functions like COUNT, SUM, or AVG operate on each group independently. A subtle behavior is that any column in the SELECT list that is not part of an aggregate function must appear in the GROUP BY clause; otherwise, most SQL engines will raise an error. In real-world scenarios, this query would be written as: SELECT customer_id, COUNT(*) FROM orders WHERE order_date >= DATE_SUB(CURDATE(), INTERVAL 1 YEAR) GROUP BY customer_id HAVING COUNT(*) > 5;
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the DA0-001 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
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FAQ
Comparing and Contrasting Data Concepts — This question tests Comparing and Contrasting Data Concepts — Read the scenario before looking for a memorised answer..
The correct answer is: Aggregation with GROUP BY — Option D is correct because the requirement to count orders per customer requires grouping rows by customer_id and then applying a count function. The GROUP BY clause in SQL aggregates rows that share a common value (customer_id) into summary rows, and the COUNT function tallies the number of orders per group. This is the standard approach for such 'per-customer' aggregations.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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