Book Image

jOOQ Masterclass

By : Anghel Leonard
Book Image

jOOQ Masterclass

By: Anghel Leonard

Overview of this book

jOOQ is an excellent query builder framework that allows you to emulate database-specific SQL statements using a fluent, intuitive, and flexible DSL API. jOOQ is fully capable of handling the most complex SQL in more than 30 different database dialects. jOOQ Masterclass covers jOOQ from beginner to expert level using examples (for MySQL, PostgreSQL, SQL Server, and Oracle) that show you how jOOQ is a mature and complete solution for implementing the persistence layer. You’ll learn how to use jOOQ in Spring Boot apps as a replacement for SpringTemplate and Spring Data JPA. Next, you’ll unleash jOOQ type-safe queries and CRUD operations via jOOQ’s records, converters, bindings, types, mappers, multi-tenancy, logging, and testing. Later, the book shows you how to use jOOQ to exploit powerful SQL features such as UDTs, embeddable types, embedded keys, and more. As you progress, you’ll cover trending topics such as identifiers, batching, lazy loading, pagination, and HTTP long conversations. For implementation purposes, the jOOQ examples explained in this book are written in the Spring Boot context for Maven/Gradle against MySQL, Postgres, SQL Server, and Oracle. By the end of this book, you’ll be a jOOQ power user capable of integrating jOOQ in the most modern and sophisticated apps including enterprise apps, microservices, and so on.
Table of Contents (26 chapters)
1
Part 1: jOOQ as a Query Builder, SQL Executor, and Code Generator
4
Part 2: jOOQ and Queries
11
Part 3: jOOQ and More Queries
16
Part 4: jOOQ and Advanced SQL
22
Part 5: Fine-tuning jOOQ, Logging, and Testing

Grouping, filtering, distinctness, and functions

In this section, grouping refers to the usage of GROUP BY with functions, filtering refers to the usage of the FILTER clause with functions, and distinctness refers to aggregate functions on distinct values.

Grouping

As you already know, GROUP BY is a SQL clause useful for arranging rows in groups via one (or more) column given as an argument. Rows that land in a group have matching values in the given columns/expressions. Typical use cases apply aggregate functions on groups of data produced by GROUP BY.

Important Note

Especially when dealing with multiple dialects, it is correct to list all non-aggregated columns from the SELECT clause in the GROUP BY clause. This way, you avoid potentially indeterminate/random behavior and errors across dialects (some of them will not ask you to do this (for example, MySQL), while others will (for example, Oracle)).

jOOQ supports GROUP BY in all dialects, therefore here is an example...