๐๏ธ How to Approach SQL Problems
When you see a SQL question, don't try to write the complete query at once.
Instead, break the problem into smaller steps and build the query logically.
๐ 1. Understand the Requirement
First, identify exactly what the question wants as the final output.
Example:
ยซFind the total revenue generated by each product.ยป
You need to display:
๐ Product
๐ Total Revenue
---
๐ 2. Identify the Required Table(s)
Find where the required data is stored.
Suppose you have:
"orders"
- product_id
- quantity
- price
- order_date
The required information is available in the "orders" table.
---
๐ 3. Identify the Required Columns
Don't select unnecessary columns.
For total revenue, you need:
"quantity ร price"
Therefore:
๐ "product_id"
๐ "quantity"
๐ "price"
---
๐ 4. Check for Filtering
Ask yourself:
ยซDo I need only specific rows?ยป
For example:
ยซFind the revenue generated during 2026.ยป
You would need:
WHERE order_date >= '2026-01-01'
๐ก WHERE filters rows before aggregation.
---
๐ 5. Look for GROUP BY Keywords
Words such as:
โข Each
โข Per
โข By
โข For every
often indicate that "GROUP BY" is required.
Example:
ยซFind revenue for each product.ยป
GROUP BY product_id
---
๐ 6. Choose the Correct Aggregate Function
Look for keywords in the question:
Total โ "SUM()"
Average โ "AVG()"
Number of records โ "COUNT()"
Highest โ "MAX()"
Lowest โ "MIN()"
For total revenue:
SUM(quantity * price)
---
๐ 7. Build the Query Step by Step
Don't jump directly to the final query.
Step 1 โ Select the required column
SELECT product_id
FROM orders;
Step 2 โ Add the calculation
SELECT
product_id,
SUM(quantity * price) AS total_revenue
FROM orders;
Step 3 โ Add grouping
SELECT
product_id,
SUM(quantity * price) AS total_revenue
FROM orders
GROUP BY product_id;
Now the basic query is complete. โ
---
๐ 8. Know When to Use HAVING
Suppose the question is:
ยซFind products whose total revenue is greater than โน50,000.ยป
Since the condition is applied to an aggregate result, use "HAVING":
SELECT
product_id,
SUM(quantity * price) AS total_revenue
FROM orders
GROUP BY product_id
HAVING SUM(quantity * price) > 50000;
๐ง Remember:
"WHERE" โ filters individual rows
"HAVING" โ filters grouped results
---
๐ 9. Check Whether a JOIN Is Required
Suppose the question asks:
ยซDisplay product names along with their total revenue.ยป
You have:
"products"
- product_id
- product_name
"orders"
- product_id
- quantity
- price
You need to connect the two tables:
SELECT
p.product_name,
SUM(o.quantity * o.price) AS total_revenue
FROM products p
JOIN orders o
ON p.product_id = o.product_id
GROUP BY p.product_name;
---
๐ 10. Check for Advanced SQL Concepts
Some problems require more than basic clauses.
Before finalizing your query, ask:
๐ Do I need a "JOIN"?
๐ Do I need "GROUP BY"?
๐ Do I need "HAVING"?
๐ Do I need "ORDER BY"?
๐ Do I need "LIMIT"?
๐ Do I need a subquery?
๐ Would a CTE make the query easier?
๐ Do I need a window function?
---
๐ง SQL Problem-Solving Framework
Whenever you get a SQL question, think in this order:
Understand โ Tables โ Columns โ JOIN โ WHERE โ GROUP BY โ Aggregate โ HAVING โ ORDER BY โ Window Functions โ Validate
โก Don't memorize SQL queries. Learn how to build them logically.
๐ Save this framework for your next SQL interview.
August 24, 2026 1.2K 9
