SQL Interview Guide with Query Practice

About this product

SQL Master Guide: 1000 Questions & Answers + Query Practice is a practice book for anyone who wants to learn SQL by doing it. It covers 20 topics in three levels (Beginner, Intermediate and Advanced). Every topic follows the same simple pattern, so you always know what to do next.

What you get in every topic:

A short theory section with a worked example
10 fill-in-the-blank questions
15 multiple-choice questions
25 interview questions with clear answers
8 to 11 SQL query problems, with the solution printed directly below each question (for example, “Find the 2nd highest salary”)
An answer key for the fill-in-the-blank and multiple-choice questions

What makes it different:

It does not stop at theory and multiple choice. You also write real queries, then compare them with the solutions.
Many solutions show the sample output, so you can check your result.
Where MySQL, PostgreSQL, SQL Server and Oracle differ, the book shows both versions (for example LIMIT vs TOP, or EXCEPT vs MINUS).
Every example uses the same two small practice tables (employees and departments), so you can set them up once and run everything.
It ends with 20 classic interview query problems, a dialect comparison sheet and a 4-week study plan.

It is suited to students, job seekers preparing for SQL interviews, and developers or analysts who want a structured refresher.

What you will learn

• Learning Outcomes
• After working through this book, you will be able to:
• Explain core database concepts: tables, keys, schemas, SQL vs NoSQL, and the DDL, DML, DQL, DCL and TCL command groups
• Write queries that filter, sort, group and summarize data using WHERE, ORDER BY, GROUP BY, HAVING and aggregate functions
• Handle NULL values correctly and choose the right data types
• Create and change tables, and add, update and delete data safely
• Design tables with primary keys, foreign keys and constraints
• Combine data from several tables with INNER, LEFT, RIGHT, FULL, CROSS and self joins
• Use subqueries and set operations (UNION, INTERSECT, EXCEPT) to answer multi-step questions
• Find the 2nd or Nth highest salary, duplicates, top-N per group and similar interview problems in several ways
• Transform data with string, date and numeric functions and CASE expressions
• Create views and indexes, and read a query’s execution plan to improve performance
• Use window functions (ranking, running totals, LAG/LEAD) and recursive CTEs for analysis and hierarchies
• Explain ACID and write safe transactions with COMMIT, ROLLBACK, savepoints and locking
• Normalize a database to 3NF and model one-to-one, one-to-many and many-to-many relationships
• Write stored procedures, functions and triggers, and prevent SQL injection with parameterized queries
• Answer common SQL interview questions confidently and adapt your queries across MySQL, PostgreSQL, SQL Server and Oracle

Contents

1. Introduction to Databases and SQL
2. SELECT, DISTINCT and Aliases
3. WHERE Clause and Operators
4. ORDER BY, LIMIT and TOP
5. Aggregate Functions
6. GROUP BY and HAVING
7. Data Types and NULL
8. DDL: CREATE, ALTER, DROP, TRUNCATE
9. DML: INSERT, UPDATE, DELETE
10. Constraints and Keys
11. JOINs
12. Set Operations and Subqueries
13. String, Date and Numeric Functions
14. CASE and Conditional Logic
15. Views, Indexes and Performance
16. Window Functions
17. CTEs and Recursive Queries
18. Transactions, ACID and Locking
19. Normalization and Database Design
20. Stored Procedures, Triggers, Functions
21. Advanced SQL

Licence and usage

Personal, non-transferable licence for your own use. Redistribution is not permitted. See the terms and refund policy.