Create an SQL Query for This Business Problem: A Practical Guide for Data Analysts?

SQL interviews are not only about remembering commands like SELECT, WHERE, or JOIN. In many Data Analyst interviews, you are given a business problem and asked to convert it into an SQL query.

This tests whether you can understand the business requirement, identify the right data, and use SQL to generate a meaningful answer.

For example, instead of asking:

“Write a query using GROUP BY.”

An interviewer may ask:

“Which products generated the highest revenue last month?”

Now you need to understand the problem first and then build the SQL query.

1. What Does a Business Problem Mean in SQL?

A business problem is a real-world question that a company wants data to answer.

Some common examples are:

Business Problem	SQL Requirement
Find the best-selling products	GROUP BY, SUM(), ORDER BY
Find customers who haven’t purchased recently	LEFT JOIN, date filtering
Calculate monthly revenue	Date functions + GROUP BY
Find employees earning above average	Subquery / CTE
Identify duplicate customers	GROUP BY, HAVING
Find the second-highest salary	DENSE_RANK() / subquery
Calculate customer retention	CTEs + date logic

The important skill is converting the business question into a data question.

2. Start by Understanding the Business Question?

Before writing SQL, break the problem into smaller parts.

Suppose the business problem is:

“Find the top 5 products by total sales.”

Ask yourself:

• Which table contains product information?
• Which table contains sales?
• What column represents sales amount?
• Do we need product-wise aggregation?
• How should the results be sorted?
• How many records should be returned?

This gives you a logical path before you write the query.

3. Example Dataset:

Imagine we have a table called sales.

sale_id	product	quantity	price	sale_date
101	Laptop	2	60000	2026-09-01
102	Mouse	10	800	2026-09-02
103	Laptop	1	60000	2026-09-03
104	Keyboard	5	1500	2026-09-04
105	Mouse	8	800	2026-09-05

Suppose the business asks:

“Which products generated the highest revenue?”

Revenue can be calculated as:

Revenue = Quantity × Price

4. Convert the Problem into SQL Logic.

Before writing the final query, identify the required steps:

1. Calculate revenue for every sale.
2. Group the data by product.
3. Add revenue for each product.
4. Sort products by revenue in descending order.
5. Return the required number of products.

The SQL query can be:

SELECT
    product,
    SUM(quantity * price) AS total_revenue
FROM sales
GROUP BY product
ORDER BY total_revenue DESC;

This query answers the business question directly.

5. Want Only the Top 5 Products?

If the business asks for only the top five products, add LIMIT:

SELECT
    product,
    SUM(quantity * price) AS total_revenue
FROM sales
GROUP BY product
ORDER BY total_revenue DESC
LIMIT 5;

For SQL Server, you can use:

SELECT TOP 5
    product,
    SUM(quantity * price) AS total_revenue
FROM sales
GROUP BY product
ORDER BY total_revenue DESC;

The syntax may change depending on the database system, but the business logic remains the same.

6. A Common Interview Business Problem

Let’s take another example.

Business Question:

“Find customers who have placed more than 3 orders.”

Suppose we have an orders table:

order_id	customer_id	order_date	amount
1	101	2026-09-01	5000
2	101	2026-09-05	3000
3	102	2026-09-06	2500
4	101	2026-09-10	4500
5	101	2026-09-15	2000

The business requirement is to count orders for each customer and return customers with more than three orders.

SELECT
    customer_id,
    COUNT(order_id) AS total_orders
FROM orders
GROUP BY customer_id
HAVING COUNT(order_id) > 3;

Notice the use of HAVING.

Why HAVING instead of WHERE?

WHERE filters individual rows before aggregation.

HAVING filters groups after aggregation.

Clause	Purpose
WHERE	Filters individual records
GROUP BY	Creates groups
HAVING	Filters aggregated groups
ORDER BY	Sorts the result

This distinction is frequently tested in SQL interviews.

7. Business Problem Involving Multiple Tables

Real company data is often distributed across multiple tables.

For example:

customers

customer_id	customer_name
101	Rahul
102	Priya
103	Amit

orders

order_id	customer_id	amount
1	101	5000
2	102	3000
3	101	4000

Business question:

“Find the total amount spent by each customer.”

You need to connect the two tables using customer_id.

SELECT
    c.customer_id,
    c.customer_name,
    SUM(o.amount) AS total_spent
FROM customers c
JOIN orders o
    ON c.customer_id = o.customer_id
GROUP BY
    c.customer_id,
    c.customer_name;

Here, the important concept is not just the JOIN.

You need to understand why the JOIN is required.

8. A Simple Framework for Business SQL Problems

When you receive a business problem in an interview, use this framework:

Business Question → Data → Filters → Joins → Aggregation → Calculation → Sorting → Final Output

For example:

Question: Find monthly revenue.

Think:

• Data → sales table
• Date → sale date
• Calculation → quantity × price
• Aggregation → SUM()
• Grouping → month
• Output → monthly revenue

Then build the query.

9. Common SQL Functions Used in Business Problems

Requirement	SQL Concept
Filter records	WHERE
Combine tables	JOIN
Calculate total	SUM()
Calculate average	AVG()
Count records	COUNT()
Find highest value	MAX()
Find lowest value	MIN()
Group results	GROUP BY
Filter groups	HAVING
Sort results	ORDER BY
Return top records	LIMIT / TOP
Categorize values	CASE
Compare rows	Window Functions
Create temporary logic	CTE

10. Don’t Write SQL Before Understanding the Problem

One of the most common mistakes beginners make is immediately starting with:

SELECT *
FROM table_name;

Instead, first understand what the business actually wants.

For example:

Business Problem:
“Which customers have not purchased anything in the last 90 days?”

This requires more thinking than simply selecting records.

You may need:

• Customer table
• Order table
• A LEFT JOIN
• Date filtering
• Handling customers with no orders
• Possibly MAX(order_date)

A possible approach is:

SELECT
    c.customer_id,
    c.customer_name
FROM customers c
LEFT JOIN orders o
    ON c.customer_id = o.customer_id
GROUP BY
    c.customer_id,
    c.customer_name
HAVING
    MAX(o.order_date) < CURRENT_DATE - INTERVAL '90 days'
    OR MAX(o.order_date) IS NULL;

The exact date syntax can vary between databases such as MySQL, PostgreSQL, and SQL Server.

11. How to Explain Your SQL Query in an Interview

Don’t simply write the query and stop.

Explain your approach.

For example:

“First, I joined the customer and order tables using customer_id. Then I grouped the data by customer so I could calculate the latest order date for each customer. Finally, I filtered customers whose latest purchase was more than 90 days ago or who had never placed an order.”

This demonstrates that you understand the business logic behind the SQL, not just the syntax.

12. Key Takeaways

When solving SQL business problems:

• Understand the business question first.
• Identify the tables and required columns.
• Determine whether a JOIN is required.
• Apply filters using WHERE.
• Use aggregation when the question requires totals, counts, or averages.
• Use GROUP BY for grouped analysis.
• Use HAVING to filter aggregated results.
• Use window functions when row-level and aggregate information are needed together.
• Check whether NULL values affect the result.
• Explain your reasoning along with your query.
• Always validate whether the output actually answers the business question.

SQL interviews are less about memorizing hundreds of queries and more about thinking logically about data.

If you can take a business question and systematically convert it into SQL, you are developing one of the most important skills required for a Data Analyst role.

Frequently Asked Questions

1. How do I start an SQL query from a business problem?

First identify what the business wants to know, then determine the required tables, columns, filters, calculations, grouping, and sorting.

2. What SQL topics are most useful for business problems?

Important topics include JOIN, GROUP BY, WHERE, HAVING, aggregate functions, subqueries, CTEs, CASE, and window functions.

3. Why are SQL business problems common in Data Analyst interviews?

Because they test whether you can convert real-world business requirements into useful data insights rather than only remembering SQL syntax.

4. Should I explain my SQL query during an interview?

Yes. Explain the logic behind your query, including why you selected particular tables, joins, filters, and calculations.

5. Can one business problem have multiple SQL solutions?

Yes. The same requirement can often be solved using joins, subqueries, CTEs, or window functions. The important part is that the logic produces the correct result and is appropriate for the database and requirement.