Learning Spring Boot from Zero to Cloud: Part 33 – JdbcTemplate – Complex Queries!

Welcome to this deep-dive tutorial where we explore how to handle complex SQL result sets using JdbcTemplate in Spring Boot. If you’ve ever struggled with joins, nested mappings, or organizing your domain models cleanly — this is the video for you.

We’ll walk through practical examples using LEFT JOIN, LinkedHashMap, and best practices for avoiding common pitfalls like N+1 problems and overfetching. By the end, you’ll know how to map parent-child relationships (like Category → Transactions) efficiently and cleanly.

📌 What you’ll learn in this video:

✨ What JdbcTemplate is and how it processes SQL queries
🛠️ How to map simple and complex results using RowMapper and ResultSetExtractor
🧠 How to structure domain models for 1:N relationships
🗂️ Best practices for deduplication and insertion order with LinkedHashMap
🚫 Anti-patterns to avoid when mapping joins
💡 Practical advice for writing cleaner, scalable query logic

⏱️ Timestamps:
00:00 – Introduction
00:32 – What is JdbcTemplate and how it works internally
03:16 – Mapping simple results with BeanPropertyRowMapper
04:43 – Handling JOINs with custom RowMapper
08:02 – Mapping nested data using LinkedHashMap
11:52 – Best practices and common mistakes
17:52 – When to switch to other tools like JPA or Spring Data JDBC
20:46 – Code walkthrough and examples