How do UPSERT and MERGE work in Oracle, SQL Server, PostgreSQL and MySQL

Introduction

Last week, Burkhard Graves asked me to answer the following StackOverflow question:

And, since he wasn’t convinced about my answer:

I decided to turn it into a dedicated article and explain how UPSERT and MERGE work in the top 4 most common relational database systems: Oracle, SQL Server, PostgreSQL, and MySQL.

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How to map Java and SQL arrays with JPA and Hibernate

Introduction

Hibernate custom Types allow you to map all sorts of database specific column types, like IP address, JSON columns, bit sets or SQL arrays.

There are two ways to define a custom Hibernate Type:

The latter option is preferred since it allows you to better split the Java-to-JDBC and the JDBC-to-SQL type handling. In this article, we are going to see how you can map SQL arrays to their Java counterpart.

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How to install DB2 Express-C on Docker and set up the JDBC connection properties

Introduction

While developing Hibernate, I need to test the code base against a plethora of relational database systems: Oracle, SQL Server, PostgreSQL, MySQL, MariaDB, Informix, and of course DB2.

However, having all these databases installed on my system is far from ideal, so I rely a lot on Docker for this task. In this article, I’m going to show how easily you can install DB2 on Docker and set up the JDBC connection so that you can run Hibernate tests on DB2.

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How does a relational database work

Introduction

While doing my High-Performance Java Persistence training, I came to realize that it’s worth explaining how a relational database works, as otherwise, it is very difficult to grasp many transaction-related concepts like atomicity, durability, and checkpoints.

In this post, I’m going to give a high-level explanation of how a relational database works internally while also hinting some database-specific implementation details.

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