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Tag Archives: Databases

JDBC Tutorial – The ULTIMATE Guide (PDF Download)

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This tutorial is about JDBC (Java Database Connectivity), an API provided by Oracle that allows programmers to handle different databases from Java applications: it allows developers to establish connections to databases, defines how a specific client can access a given database, provides mechanisms for reading, inserting, updating and deleting entries of data in a database and takes care of transactions ...

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Declarative SQL Mode Pitfall

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As we know a view object definition supports three SQL modes. There are normal, declarative and expert modes. In this post I’m going to focus on the declarative SQL mode. This smart mode allows the framework to automatically build SQL queries at run time according to the attributes asked by the view layer. Furthermore, depending on the attributes being asked, the frameworks ...

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Leaky Abstractions, or How to Bind Oracle DATE Correctly with Hibernate

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We’ve recently published an article about how to bind the Oracle DATE type correctly in SQL / JDBC, and jOOQ. This article got a bit of traction on reddit with an interesting remark by Vlad Mihalcea, who is frequently blogging about Hibernate, JPA, transaction management and connection pooling on his blog. Vlad pointed out that this problem can also be ...

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A beginner’s guide to transaction isolation levels in enterprise Java

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Introduction A relational database strong consistency model is based on ACID transaction properties. In this post we are going to unravel the reasons behind using different transaction isolation levels and various configuration patterns for both resource local and JTA transactions.           Isolation and consistency In a relational database system, atomicity and durability are strict properties, while ...

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Adding OpenSSL User-Defined Types to PostgreSQL

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PostgreSQL supports user-defined types (UDT). These types can be used to provide type-safety on user-defined functions when we would otherwise be forced to use simple BLOB objects. This comes at a significant cost. Many databases support UDT but implementation details vary widely so there’s a significant amount of vendor lock-in. In addition C language UDT require deployment via PostgreSQL extensions ...

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Database Threat Models

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I finally have a breather and can start working through my backlog of ideas. I start with some background that will make the motivation for subsequent posts clearer. What are the threat models for the persistence layer of an application, specificially the threats against the database itself? Remember that a ‘threat’ is an adverse act, whether intentional (by an attacker) ...

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Do You Really Understand SQL’s GROUP BY and HAVING clauses?

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There are some things in SQL that we simply take for granted without thinking about them properly. One of these things are the GROUP BY and the less popular HAVING clauses. Let’s look at a simple example. For this example, we’ll reiterate the example database we’ve seen in this previous article about the awesome LEAD(), LAG(), FIRST_VALUE(), LAST_VALUE() functions:   ...

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