Tag Archives: SQL

You can define and link to SQL scripts in a JPA persistence context definition that will be executed at runtime. There are standardized properties to define scripts how to create the schema, bulk-load data and drop the schema, respectively: <persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"> <persistence-unit name="prod" transaction-type="JTA"> <properties> <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/> <property name="javax.persistence.schema-generation.create-script-source" value="create-schema.sql" /> <property name="javax.persistence.schema-generation.sql-load-script-source" value="load-data.sql" /> ...

One of the big advantages of using Docker for testing is that you don’t need to install the required dependencies of code under tests in all machines where you are going to run these tests. This is really helpful for external services such as database servers, mail services, JMS queues, … Also one of the big advantages of this approach is ...

Today’s modern application frameworks come with apromise of easy sql data access. There is no wonder why we have so many frameworks that make it easier to issue queries and handle transactions. SQL is the lingua franca of most applications when it comes to databases. Play comes with the JDBC plugin. We encountered the JDBC plugin previously in order to ...

Introduction Working with a team of developers often poses challenges and causes frustrations with managing the development database. There are many good approaches to solving the problems of interfering with each others’ code, but my preferred solution has become the SQL Server Database Project in Visual Studio. This article will show you how to take an existing SQL database and ...

One of the more challenging aspects of software development can be dealing with floating-point numbers. David Goldberg‘s 1991 Computing Surveys paper What Every Computer Scientist Should Know About Floating-Point Arithmetic is a recognized classic treatise on this subject. This paper not only provides an in-depth look at how floating-point arithmetic is implemented in most programming languages and computer systems, but ...

In this week’s Whiteboard Walkthrough Parth Chandra, Chair of PMC for Apache Drill project and member of MapR engineering team, describes how the Apache Drill SQL query engine reads data in Parquet format and some of the best practices to get maximum performance from Parquet. Additional Apache Drill resources: ”Overview Apache Drill’s Query Execution Capabilities” Whiteboard Walkthrough video “SQL Query ...

There are a couple of ways to remove duplicate rows from a table in SQL e.g. you can use a temp tables or a window function like row_number() to generate artificial ranking and remove the duplicates. By using a temp table, you can first copy all unique records into a temp table and then delete all data from the original table ...

This post will use Apache Spark SQL and DataFrames to query, compare and explore S&P 500, Exxon and Anadarko Petroleum Corporation stock prices for the past 5 years. Stocks and oil prices have a tendency to move together over the past decade as explained in this blog post from Ben Bernanke.                 The ...

You may have heard this statement before:      Apache Drill does schema discovery on-the-fly. What does that mean, and why should it matter to you? The power of SQL for business analytics is a given, but the challenge in big data settings is that SQL is normally a static language that assumes pre-defined, fixed and well-known schema. SQL also needs flat ...