Mastering SQL Interviews: 15 Real-world Questions with Business Context (2025 Edition)

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Introduction

SQL remains the backbone of data manipulation and analysis across industries. In this comprehensive guide, I’ll explore 15 challenging SQL questions that frequently appear in interviews at top companies like Google, Amazon, Microsoft, and leading consulting firms. Each question includes business context, solution, and detailed explanations.

Question 1: Customer Purchase Analysis

Business Context:
An e-commerce company wants to identify its most valuable customers based on purchase patterns to create targeted marketing campaigns and loyalty programs.

Problem Statement:
Find customers who have made purchases in consecutive months and their total spending pattern.

WITH consecutive_purchases AS (
    SELECT 
        customer_id,
        purchase_date,
        purchase_amount,
        LEAD(purchase_date) OVER (PARTITION BY customer_id ORDER BY purchase_date) as next_purchase_date
    FROM customer_purchases
    WHERE purchase_date >= '2023-01-01'
)
SELECT 
    customer_id,
    COUNT(DISTINCT DATE_TRUNC('month', purchase_date)) as purchase_months,
    SUM(purchase_amount) as total_spent…