Week 3/32: Advanced SQL Concepts for Data Engineering Interviews

Week 3 of 32-Week Data Engineering Interview Guide

In the previous post, we explored SQL Fundamentals, covering essential topics such as Joins, Aggregate Functions, Subqueries, Common Table Expressions (CTEs), Date and Time Functions, and Null Values.
If you missed the previous post, you can check it out here:

Week 2/32: SQL Fundamentals for Data Engineering Interviews

The full plan for the series is as follows.

What This Post Covers

This post builds on the fundamentals by focusing on Advanced SQL Concepts through solving SQL interview questions in a structured, three-step approach:

1. Thinking Steps: We’ll walk through the thought process before solving a problem, as explaining your thoughts is a key skill for live interviews.

2. Solution Query: We’ll write the SQL solution to solve the problem efficiently.

3. Explanation: We’ll break down the solution to ensure a clear understanding of the query and its logic.

We’ll tackle SQL Interview Questions from top companies like Amazon, Apple, Microsoft, Google, PwC, Uber and so on. These questions are designed to test your technical understanding and your ability to write practical queries for real-world scenarios.

While this post primarily targets Data Engineering interviews, we believe professionals preparing for roles such as Data Analyst, Analytics Engineer or similar will also find it beneficial.

Topics included in this post:

• Set Operations

• Window Functions

• Recursive CTEs and Hierarchical Queries

• Indexes

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1. Set Operations

Set operations in SQL allow us to combine or compare the results of two or more SELECT statements, much like mathematical set operations. These operations enable powerful analysis of data from multiple sources or perspectives, making them essential tools for data manipulation in SQL.

Set operations include UNION, UNION ALL, INTERSECT, and EXCEPT, and they help in solving complex problems by comparing or merging datasets.

Here’s a quick breakdown of the core set operations: