Top SQL Questions for 5 Years Experience Candidates (Expert Level)

10 April, 2025 admin 0 Comments 1 category

If you have 5 years of experience in SQL, chances are you’re preparing for a senior role—possibly as a data analyst, backend developer, database administrator, or BI specialist. At this level, interviewers expect not just syntax knowledge, but also your ability to solve real-world problems, write optimized queries, and understand database architecture.

In this guide, we’ll explore the most common SQL questions for 5 years experience that often appear in technical interviews. Each question includes explanations and sample queries, helping you prepare with confidence.

1. Explain the Difference Between RANK(), DENSE_RANK(), and ROW_NUMBER()

These window functions are frequently asked in mid-to-senior level interviews.

Sample Query:

sqlCopyEditSELECT 
  employee_name, salary,
  RANK() OVER (ORDER BY salary DESC) AS salary_rank,
  DENSE_RANK() OVER (ORDER BY salary DESC) AS dense_salary_rank,
  ROW_NUMBER() OVER (ORDER BY salary DESC) AS row_num
FROM employees;

Why It’s Asked:
To test your understanding of window functions and how each handles duplicate values.

2. How Do You Optimize a Slow SQL Query?

This is a must-know for any professional with 5+ years of experience.

Answer Framework:

Use EXPLAIN to understand the query plan.
Create proper indexes on frequently used columns.
Avoid SELECT *, use only required columns.
Eliminate unnecessary joins or subqueries.
Use temporary tables for complex data processing.

Pro Tip: Be ready to share examples where you improved query performance.

3. Write a Query to Fetch the Second Highest Salary Without Using LIMIT or TOP

A classic trick question with multiple solutions.

Sample Query:

sqlCopyEditSELECT MAX(salary) AS second_highest
FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);

Why It’s Asked:
To test your ability to think beyond standard clauses like LIMIT.

4. How Do You Handle NULLs in Aggregate Functions?

Answer:
Functions like SUM(), AVG(), and COUNT() ignore NULLs by default.

Bonus: You can use COALESCE(column, 0) to treat NULLs as zeros.

5. Query to Find Employees Who Don’t Have a Manager

This tests your JOIN and filtering logic.

Sample Query:

sqlCopyEditSELECT e.employee_name
FROM employees e
LEFT JOIN employees m ON e.manager_id = m.employee_id
WHERE m.employee_id IS NULL;

Why It’s Asked:
To check your ability to work with self-joins and null filtering.

6. Explain the ACID Properties of a Database

ACID stands for:

Atomicity: All steps in a transaction succeed or none.
Consistency: Data must remain consistent before and after transactions.
Isolation: Transactions don’t interfere with each other.
Durability: Once a transaction is committed, it remains so—even during a crash.

7. Real-World Scenario: Partition vs Indexing

Question: When would you use table partitioning instead of indexing?

Answer: Use partitioning when dealing with very large datasets that need to be broken down (e.g., monthly logs), and indexing for quick lookup of smaller, frequently accessed columns.

8. Write a Query to Pivot Data in SQL

Scenario: Convert rows to columns (e.g., monthly sales per product).

Sample Query:

sqlCopyEditSELECT product,
  SUM(CASE WHEN month = 'Jan' THEN sales ELSE 0 END) AS Jan,
  SUM(CASE WHEN month = 'Feb' THEN sales ELSE 0 END) AS Feb
FROM sales_data
GROUP BY product;

Why It’s Asked:
Pivoting is essential for BI reporting and dashboard creation.

9. Explain CTEs (Common Table Expressions)

Use Case:
CTEs improve readability and help in recursive queries.

Sample:

sqlCopyEditWITH dept_total AS (
  SELECT department_id, COUNT(*) AS total_employees
  FROM employees
  GROUP BY department_id
)
SELECT * FROM dept_total;

10. SQL Scenario-Based Question

“You’re asked to fetch the top 3 selling products for each region. How will you do it?”

Answer Using Window Function:

sqlCopyEditSELECT *
FROM (
  SELECT product_id, region,
         RANK() OVER (PARTITION BY region ORDER BY sales DESC) AS rnk
  FROM sales
) sub
WHERE rnk <= 3;

Final Tips for SQL Interviews After 5 Years of Experience

Be prepared to explain the logic behind your answers.
Show awareness of database performance, not just correctness.
Know how to handle large datasets efficiently.
Practice writing queries by hand or in a whiteboard interview style.

FAQs: SQL Questions for 5 Years Experience

Q1. Will these questions be asked in Data Analyst roles?
Yes! Data analysts often face SQL challenges related to window functions, joins, filtering, and real-world scenarios.

Q2. How deep should I go with performance tuning?
You should at least understand indexing, query planning, and table optimization techniques.

Q3. Do these SQL questions vary by company?
Yes, but many companies like TCS, Infosys, Wipro, and MNCs ask variations of these same themes.

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