SQL JOIN USING – A Beginner’s Guide
Introduction In this article, we are going to see how the JOIN USING clause works in SQL, and how we can use it to replace the ON condition clause when the columns used to join the two tables have the same name in both the parent and the child tables.
SQL LEFT JOIN – A Beginner’s Guide
Introduction In this article, we are going to see how LEFT JOIN works in SQL, and how we can use it to associate rows belonging to different tables and build compound result sets. Unlike JOIN or INNER JOIN, LEFT JOIN is an OUTER JOIN. So, LEFT JOIN and LEFT OUTER JOIN are equivalent. Other OUTER JOIN types are RIGHT OUTER JOIN and FULL OUTER JOIN. However, since the SQL OUTER keyword is superfluous, it’s usually omitted.
How does orphanRemoval work with JPA and Hibernate
Introduction In this article, we are going to see how the JPA and Hibernate orphanRemoval mechanism allows us to trigger an entity child remove operation upon disassociating the child entity reference from the child collection on the parent side.
Flyway Database Schema Migrations
Introduction In this article, I’m going to explain how Flyway works and how you can use it to run automated database schema migrations using incremental SQL migration scripts. Flyway is an open-source project created by Axel Fontaine and later acquired by Red Gate. The database migrations can be defined either as SQL scripts or JDBC-based classes.
Java Map to JSON mapping with JPA and Hibernate
Introduction In this article, we are going to see how we can store Java Map entity attributes in JSON columns when using JPA, Hibernate, and the Hypersistence Utils project. While you can also persist Java Map entity attributes in PostgreSQL HStore columns, a JSON column type is a much more common option, especially since it works with other relational databases, like Oracle, SQL Server, or MySQL. As you already have seen, the Hypersistence Utils project allows you to map a JSON column type to a wide variety of JPA entity attributes, like… Read More
Read-write and read-only transaction routing with Spring
Introduction In this article, I’m going to explain how you can implement a read-write and read-only transaction routing mechanism using the Spring framework. This requirement is very useful since the Single-Primary Database Replication architecture not only provides fault-tolerance and better availability, but it allows us to scale read operations by adding more replica nodes.
JPA and Hibernate Query setParameter – User Guide
Introduction In this article, I’m going to show you how the JPA Query setParameter method works for basic entity attributes, and how you can use it when dealing with custom Hibernate types. If you ever stumbled on the “column is of type jsonb but expression is of type bytea” PostgreSQL issue and didn’t know how to fix it, then you should definitely read this article.
