SQL EXISTS and NOT EXISTS
Introduction In this article, we are going to see how the SQL EXISTS operator works and when you should use it. Although the EXISTS operator has been available since SQL:86, the very first edition of the SQL Standard, I found that there are still many application developers who don’t realize how powerful SQL subquery expressions really are when it comes to filtering a given table based on a condition evaluated on a different table.
How to return a Map result from a JPA or Hibernate query
Introduction In this article, I’m going to show you how you can return a Java Map result when executing a JPA query. I decided to write this article after answering a similar question on StackOverflow.
Multidimensional array mapping with JPA and Hibernate
Introduction In this article, I’m going to present the best way to map a Java multidimensional array when using JPA and Hibernate. While one-dimensional array types have long been supported by the Hypersistence Utils open-source project, starting with the 2.9 release, you can now persist multidimensional array entity attributes with JPA and Hibernate.
The best way to use a Hibernate ResultTransformer
Introduction In this article, I’m going to present the best way to use a Hibernate ResultTransformer so that you can customize the result set of a given JPA or Hibernate query. As I already explained, the Hibernate ResultTransformer is a very powerful mechanism, allowing you to customize a JPQL, Criteria API, or native SQL query result set in any possible way.
