SQL That Does the Work: The 20% of SQL Behind 80% of Real Queries
About this PDF
You don’t need every SQL feature to be useful at work. You need the core patterns, and you need to know where they quietly go wrong. SQL That Does the Work teaches each pattern with a query you can run, its actual output, and the traps to avoid. Every query that shows a result was run on PostgreSQL 16, and a sample database is included so you can follow along. What’s inside: 11 core chapters: filtering and aggregation, joins, CTEs, window functions, subqueries, conditional logic, dates and strings, set operations, NULLs, sorting and pagination, plus DDL, DML, transactions, and permissions 8 reusable recipes: top N per group, percentage of total, deduplication, filling date gaps, first and latest events, repeat purchase rate, monthly cohorts, and medians 10 silent bugs checklist: mistakes that raise no error but can give wrong results, such as join fan-out and NOT IN with NULLs 12 exercises with answers: from warm-ups to interview-level problems 8 interview questions: with short answers you can say out loud Quick reference: a one-page cheat sheet, a one-page map of SQL, and a table of differences across PostgreSQL, MySQL, SQL Server, and Oracle Who it’s for: developers, analysts, students, and interview candidates who know some SQL basics or are learning them, and want to write queries with confidence. About the author: Karthikeyan T is a Senior AI Engineer and SaaS Architect with 20+ years of engineering experience. Format: 40-page PDF with clickable contents, plus a .sql file with the sample database. Examples use PostgreSQL.
What you get
What’s inside
Details
- Format
- 1 PDF · 1 ZIP
- Language
- English
- Size
- 1.2 MB
- Delivery
- Download to your device, instantly after payment
- Access
- Lifetime — buy once, open any time
- Sold by
- Karthikeyan T
- Published
- 2 November 2026
