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Displaying posts with tag: postgresql (reset)
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. Oracle Since September 2019, the Oracle JDBC Driver is available on Maven Central. For JDK 10 and 11, use the following Maven dependency: For JDK 8, use the ojdbc8 artifact instead: For more details about the proper version to use, check out the following Maven Central link. MySQL The MySQL Driver is available on Maven Central, so just... Read More

The post JDBC Driver Maven dependency list appeared first on Vlad Mihalcea.

Session Variables

In MySQL and Oracle, you set a session variable quite differently. That means you should expect there differences between setting a session variable in Postgres. This blog post lets you see how to set them in all three databases. I’m always curious what people think but I’m willing to bet that MySQL is the simplest approach. Postgres is a bit more complex because you must use a function call, but Oracle is the most complex.

The difference between MySQL and Postgres is an “@” symbol versus a current_setting() function call. Oracle is more complex because it involves the mechanics in Oracle’s sqlplus shell, SQL dialect, and PL/SQL language (required to assign a value to a variable).

MySQL

MySQL lets you declare a session variable in one step and use it one way in a SQL statement or stored procedure.

  1. You set a session variable on a single line with the following …
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Join Pythian for Percona Live Europe 2019 Amsterdam

Percona Live is always a great opportunity to learn from the best and brightest in the open-source database community. This time, Percona Live Europe is being held at the Hilton Amsterdam Airport Schiphol, The Netherlands from September 30 to October 2, 2019.

Pythian will be present, as has been the case for the past few years, with some of our technical experts speaking on a variety of subjects and technologies.

Feel free to ping any of us during the conference breaks or community events, as we’ll be happy to answer any questions you have about anything open source, cloud, or data-related.

Here are some sessions you won’t want to miss:

Wednesday, October 2

9:00 AM – …

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What’s Faster? COUNT(*) or COUNT(1)?

One of the biggest and undead myths in SQL is that COUNT(*) is faster than COUNT(1). Or was it that COUNT(1) is faster than COUNT(*)? Impossible to remember, because there’s really no reason at all why one should be faster than the other. But is the myth justified?

Let’s measure!

How does COUNT(…) work?

But first, let’s look into some theory. The two ways to count things are not exactly the same thing. Why?

  • COUNT(*) counts all the tuples in a group
  • COUNT(<expr>) counts all the tuples in a group for which <expr> evaluates to something that IS NOT NULL

This distinction can be quite useful. Most of the time, we’ll simply COUNT(*) for convenience, but there are (at least) two cases where we don’t want that, for example:

When outer joining

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Entity Framework 6.3 and .NET Core 3 Support

.NET Core 3 .NET Core was presented by Microsoft in 2016, but its 1.x versions had limited set of features comparing to Full .NET Framework. Since then .NET Core has been drastically improved. .NET Core 2.0 has a significant part of Full .NET Framework features and includes new functionality and significant performance optimizations. This year, […]

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. Why limit the number of rows of a SQL query? Fetching more data than necessary is the number one cause of data access performance issues. When a given business use case is developed, the amount of data available... Read More

The post How to limit the SQL query result set to Top-N rows only appeared first on Vlad Mihalcea.

SQL ORDER BY RANDOM

Introduction In this article, we are going to see how we can sort an SQL query result set using an ORDER BY clause that takes a RANDOM function provided by a database-specific function. This is a very handy trick, especially when you want to shuffle a given result set. Note that sorting a large result set using a RANDOM function might turn out to be very slow, so make sure you do that on small result sets. If you have to shuffle a large result set and limit it afterward, then it’s... Read More

The post SQL ORDER BY RANDOM appeared first on Vlad Mihalcea.

2019 Open Source Database Report: Top Databases, Public Cloud vs. On-Premise, Polyglot Persistence

Ready to transition from a commercial database to open source, and want to know which databases are most popular in 2019? Wondering whether an on-premise vs. public cloud vs. hybrid cloud infrastructure is best for your database strategy? Or, considering adding a new database to your application and want to see which combinations are most popular? We found all the answers you need at the Percona Live event last month, and broke down the insights into the following free trends reports:

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Introducing Tungsten Replicator (AMI): The High Performance Replication Engine For MySQL, MariaDB & Percona Server

Discover Tungsten Replicator (AMI) – the replication engine for MySQL, MariaDB & Percona Server, including Amazon RDS MySQL and Amazon Aurora We’re excited to announce the availability on the Amazon Marketplace of the new Tungsten Replicator (AMI). Tungsten Replicator (AMI) is a replication engine that provides high-performance and improved replication functionality over the native MySQL replication solution and provides an ability to apply real-time MySQL data feed into a range of analytics and big data databases. Tungsten Replicator (AMI) builds on the well-established, commercial stand-alone product Tungsten Replicator and offers the exact same functionality, but with the convenience that comes with an ad-hoc online service: cost-effective and rapid, automated deployment. Target Databases Available as of Today

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Pythian will be at Percona Live 2019 – Join us in Austin, Texas!

Percona Live provides the open source database community with an opportunity to discover and discuss the latest open source trends, technologies, and innovations. The conference includes the best and brightest innovators and influencers in the open source database industry.

This year, Percona Live is being held at the Hyatt Regency in Austin, Texas from May 28-30, 2019.

Pythian is proud to be a Silver Sponsor this year, with a full force of our technical experts speaking on a variety of subjects and technologies. These are sessions you won’t want to miss!

If you’re attending, make sure you swing by our booth and meet the Pythian crew. We’ll be happy to answer any questions you have about open source, cloud or anything data related. Our speakers will also be covering the event on social media and we’ll recap the event and their talks here on the Pythian …

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