Whenever we want a query’s results sorted, you may think of using the clause “order by.” You are correct: most of the time, MySQL will return the results in expected order with “order by.”

Be careful, though. Sometimes MySQL may return results in the non-deterministic order even with “order by.”

Indeed, if a query is ordered by a non-unique column, it may return results in an unexpected order. I tested the below example on MySQL 5.1.73, 5.5.54 and 5.6.19 and got the same result. However, when I applied the same example on MySQL 5.7.17, it returned the results in an unexpected order differently.

Follow me step-by-step and see how MySQL returns results in a non-deterministic order. Step 1-4 is for MySQL 5.1.73, 5.5.54 and 5.6.19, Step 5 is for MySQL 5.7.17. After the example, I will explain the reason behind this output.

Step 1. Create the table as …

Introduction As previously explained, you can run database integration tests 20 times faster! The trick is to map the data directory in memory, and my previous article showed you what changes you need to do when you have a PostgreSQL or MySQL instance on your machine. In this post, I’m going to expand the original … Continue reading How to run integration tests at warp speed using Docker and tmpfs →

As a part database administration, DBA has to take care of sub-components of database like server logs and has to plan for maintenance activity for these components regularly.

MySQL has various types of log i.e binary log, error log, slow query log, general log for different purposes. And after certain time these logs will grow and you will start seeing issues like low disk space, a large number of logs etc.

MySQL allows you to flush logs using flush logs command, next “How to rotate and clean up old MySQL logs? ”

Linux has a utility called “logrotate” , using logrotate we can implement log rotation for MySQL server logs.

Binary logs: This one is critical if you have replication setup, By enabling  expire_logs_days mysql variable you can manage …

Percona is calling on you! Vote for Percona for Database of the Year in LinuxQuestions.org Members Choice Awards 2016. Help Percona get recognized as one of the best database options for data performance. Percona provides free, fully compatible, enhanced, open source drop-in replacement database software with superior performance, scalability and instrumentation.

LinuxQuestions.org, or LQ for short, is a community-driven, self-help website for Linux users. Each year, LinuxQuestions.org holds an annual competition to recognize the …

It's not always obvious what makes one database type distinct from another. What are the most significant ways that Amazon Aurora is different from MySQL? Clear separators aren't always featured or widely known, but even slight variables between two databases can prove valuable in choosing which one is right for you and your organization.

In the case of Aurora, there are at least three interesting things that make it unique and that present opportunities for particular uses. (Thanks in advance to @saileshkrish for helping us stay in-the-know on what Aurora can do.)

Adaptive Thread Pool

wow pic.twitter.com/KeVY5VBEMS

— Preetam (@PreetamJinka) December 21, 2016

Aurora's thread pool …

In my previous post, we saw the usage of MySQL Group Replication (MGR) in single-primary mode. We know that Oracle does not recommends using MGR in multi-primary mode, but there is so much in the documentation and in presentations about MGR behavior in multi-primary, that I feel I should really give it a try, and especially compare this technology with the already existing multiple master solution introduced in 5.7: multi-source replication.

Installation

To this extent, I will set up two clusters using MySQL-Sandbox. The instructions for MGR in …

Overview

MySQL Group Replication was released as GA with MySQL 5.7.17. It is essentially a plugin that, when enabled, allows users to set replication with this new way.

There has been some confusion about the stability and usability of this release. Until recently, MySQL Group Replication (MGR) was only available in the Labs, which traditionally denotes a preview or an use-at-your-own-risk feature. Several months ago we saw the release of Group Replication as a Docker image, which allowed users to deploy a peer-to-peer cluster (every node is a master.) However, about one month after such release, word came from Oracle discouraging this setup, and inviting users to use Group Replicator in …

Recently I was testing data migration from MSSQL to MySQL using MySQL Workbench. My aim was to include data with all datatype available in MSSQL for migration. In this following blog post will see data migration prerequisites, migration steps and few common errors.

• About MySQL Workbench
• Prerequisite
• DATA SOURCE ODBC Configuration
• Required privileges on MS-SQL DB
• DB Servers Data Types …

This blog discusses how to prepare your database for the new leap second coming in the new year.

At the end of this year, on December 31, 2016, a new leap second gets added. Many of us remember the huge problems this caused back in 2012. Some of our customers asked how they should prepare for this year’s event to avoid any unexpected problems.

It’s a little late, but I thought discussing the issue might still be useful.

The first thing is to make sure your systems avoid the issue with abnormally high CPU usage. This was an problem in 2012 due to a Linux kernel bug. After the leap second was added, CPU utilization sky-rocketed on many systems, taking down …

Take Percona’s blog poll on what programming languages you’re using for backend development.

While customers and users focus and interact with applications and websites, these are really just the tip of the iceberg for the whole end-to-end system that allows applications to run. The backend is what makes a website or application work. The backend has three parts to it: server, application, and database. A backend operation can be a web application communicating with the server to make a change in a database stored on a server. Technologies like PHP, Ruby, Python, and others are the ones backend programmers use to make this communication work smoothly, allowing the customer to purchase his or her ticket with ease.

Backend programmers might not get a lot of credit, but they are the ones that design, …