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.
SQL CROSS JOIN – A Beginner’s Guide
Introduction In this article, we are going to see how a CROSS JOIN works, and we will also make use of this SQL join type to build a poker card game.
PostgreSQL trigger consistency check
Introduction In this article, we are going to see how to implement a non-trivial consistency check using a PostgreSQL INSERT and UPDATE trigger. By using a database trigger after executing an INSERT or UPDATE, we can ensure that the sum of salaries in a given department does not exceed the maximum budget allocated for the given department.
A beginner’s guide to database deadlock
Introduction In this article, we are going to see how a deadlock can occur in a relational database system, and how Oracle, SQL Server, PostgreSQL, or MySQL recover from a deadlock situation.
JDBC Driver Maven dependency list
Introduction Ever wanted to connect to a relational database using Java and didn’t know which JDBC Driver Maven dependency to use? If so, this article is surely going to help you from now on.
Mapping PostgreSQL Interval to Java Duration with Hibernate
Introduction In this article, we are going to see how to map the PostgreSQL interval column type to a Java Duration object using Hibernate and the Hypersistence Utils project. Another very useful feature introduced by the Hypersistence Utils project is that all types extending the ImmutableType can now be treated as standard org.hibernate.type.Type, therefore enabling a much better Hibernate Core API integration.
How to limit the SQL query result set to Top-N rows only
Introduction In this article, we are going to see how we can limit the SQL query result set to the Top-N rows only. Limiting the SQL result set is very important when the underlying query could end up fetching a very large number of records, which can have a significant impact on application performance.
