Introduction

About this course

This advanced module in the SQL Interview Prep series focuses on real-world, senior-level SQL topics commonly tested in interviews. We will work on robust transaction control, stored routines, flow control and validation, advanced database objects, plan analysis and optimizer influence, SQL modes and permissions, as well as reliable data import and export. The course uses MySQL 8.0 as its baseline, and whenever syntax or features differ across popular DBMS, we will review practical alternatives.

Database used in this course

We will practice on a production-style OnlineStore schema that includes categories, products, customers, suppliers, orders, order line items, and supplier mappings. It contains helpful generated or derived fields so that performance, validation, and auditing exercises feel realistic.

How the lessons work

Each question lesson is independent. Attempt the problem first, then review the matching solution lesson with line-by-line explanations, variations, and similar questions to deepen your understanding.

Course structure and practice approach

This course is structured around the most frequently asked SQL interview questions. We will attempt these questions to refine our query writing skills. Correct answers and similar questions are provided in the solution lessons. Each lesson includes interactive widgets that allow us to practice and sharpen our skills. Because every lesson is independent, we can move freely across the course in any order.

The questions in this course are based on realistic business scenarios using a single dataset that includes the Categories, Products, Customers, Suppliers, Orders, OrderDetails, and Product_Suppliers tables. This approach allows us to reuse a consistent schema to solve a wide range of problems.

What you will learn

You will learn the following concepts:

• Transactions and execution control: Define precise units of work, including locks, savepoints, and isolation levels, so queries behave predictably under concurrency.

• Stored routines: Use parameters, variables, conditionals, loops, cursors, and stored functions to safely encapsulate business rules.

• SQL flow control and validation: Apply common table expressions, view-based validation, and error handling patterns inside routines.

• Advanced database objects: Use window functions, partitioning, triggers, and cascades to enforce rules and scale access.

• Query plans and performance: Focus on reading EXPLAIN, shaping plans with hints, and influencing the optimizer responsibly.

• SQL modes and permissions: Control SQL behavior, manage read locking, differentiate table-level vs. row-level locks, and apply a principled approach to grants.

• Data import and export: Use dependable JSON and CSV workflows that you can script and automate.

Here’s what you’ll be able to do by the end of this course:

• Diagnose and fix locking and isolation issues.

• Package business logic in routines with robust error handling and validation.

• Read and shape query plans to meet service-level goals.

• Enforce security with SQL modes and least-privilege grants.

• Move data in and out of the database reliably for analytics and integrations.

Who should take this course

This course is designed for engineers preparing for senior or lead data and backend roles, and practitioners who already write complex queries and want confidence with performance tuning, concurrency control, and secure operations in interviews and production.

Prerequisites

You should be comfortable with joins, aggregates, grouping, filtering, date and time work, constraints, indexing, views, stored procedures, subqueries, and window functions. We also recommend completing the previous modules in the SQL Interview Prep series:

• SQL Interview Preparation

• SQL Interview Prep - Intermediate

You may also explore the Grokking the SQL Interview Patterns course for advanced problem-solving techniques.

With this foundation, you are ready to take your SQL skills to the next level.