When you work with complicated queries, especially ones which contain subqueries, it is easy to make a typo or misinterpret column name. While in many cases you will receive a 

column not found

 error, sometimes you can get strange results instead.

Like finding 4079 countries in Antarctica:

mysql> select count(*) from City where CountryCode in (select CountryCode from Country where Continent = 'Antarctica');
+----------+
| count(*) |
+----------+
|     4079 |
+----------+
1 row in set (0.05 sec)

Or not finding any cities in Georgia:

mysql> select Name, Language from City join CountryLanguage using (CountryCode) where CountryCode in (select Code from Country where District='Georgia' and Continent='Asia');
Empty set (0.18 sec)

I used a standard …

Data is the most important asset any organization has especially those who belongs to web, mobile, social, enterprise and cloud applications.

Availability refers to the ability to cope with, and if necessary recover from, failures on the host, including failures of MySQL, the operating system, or the hardware and maintenance activity that may otherwise cause downtime.

Because each application has different operational and availability requirements, MySQL offers a range of certified and supported solutions, delivering the appropriate levels of High Availability (HA). 

Factors to consider for HA Solution: 

• Operational Capabilities
• Budgetary Constraints
• The level of availability required (In terms of Time)
• The type of application being deployed
  • Mission critical services …

UK server monitoring platform provider moves from MySQL to MariaDB with ClusterControl

Stockholm, Sweden and anywhere else in the world - 08 December 2015 – Severalnines, the provider of open source database management tools, today announced its latest customer, CloudStats.me. CloudStats.me is a cloud-based server monitoring platform capable of monitoring Linux, Windows, OS X servers and personal computers, web sites and IP addresses. Users of CloudStats.me range from system administrators to website owners and web hosting providers, such as WooServers, HudsonValleyHost and other SMEs.

CloudStats.me is a UK company which currently monitors more than 1300 servers and 1000 websites and its server monitoring platform is growing rapidly at 500-1000 new users per week, adding approximately 1.5 servers to each new user …

I am a MySQL DBA role as usual check the problems and seek a solution.
On one of the production host (MySQL v5.1.53), I started getting errors in this series:

[Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'binlog.000942' at postion 45042

[ERROR] Error reading packet from server: Lost connection to MySQL server during query ( server_errno=2013)

[Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'binlog.000928' at postition

[ERROR] Error reading packet from server: Lost connection to MySQL server during query ( server_errno=2013)

…

Some expert says you should increase the slave_net_timeout and some says to check value of  relay_log_space_limit but it is default already

slave_net_timeout = 3600
relay_log_space_limit = 0 (unlimited) 
max_allowed_packet = 128MB

I can see no heavy queries …

In a recent blog post my colleague Roy presented his work for MySQL 5.7 that makes the query optimizer merge sub-queries in the  FROM clause (so-called derived tables) with the outer query.  I will in this blog post show an example of how this work improves the performance of a MySQL query.…

MySQL Cluster Manager 1.4.0 is available for download from My Oracle Support.

More details are available in the the MCM 1.4.0 Release Notes.

Updated documentation is available here……

I’m pleased to announce that MySQL Connector/J 5.1.38 Maintenance Release is now generally available.

MySQL Connector/J can be downloaded from the official distribution channels MySQL Downloads and The Central repository. The commercially licensed version is available for download at My Oracle Support.

As always, we recommend that you check the CHANGES file in the download archive and/or the release notes to be aware of changes in behavior that might affect your application.

MySQL Connector/J 5.1.38, although released shortly after its predecessor, …

This and the next few posts will be on the basics of MySQL for my MySQL 101 presentation at the Rocky Mountain Oracle User Groups Training Days.Training Days 2016 : Rocky Mountain Oracle Users Group

MySQL is available from multiple sources.  It might be a part of your Linux distributions available software or already built into your virtual image if you are using something like Laravel's Homestead.  MySQL runs on most of the popular operating systems.  And it is highly recommended to start off at MySQL :: MySQL Downloads to get the latest and greatest. Don't be intimidated by the man options available to you. Most people start with the MySQL Community Edition server MySQL :: …

Requires ClusterControl 1.2.11 or later. Applies to MySQL based instances/clusters.

On some occasions, you might want to run multiple instances of MySQL on a single machine. You might want to give different users access to their own mysqld servers that they manage themselves, or you might want to test a new MySQL release while keeping an existing production setup undisturbed.

It is possible to use a different MySQL server binary per instance, or use the same binary for multiple instances (or a combination of the two approaches). For example, you might run a server from MySQL 5.1 and one from MySQL 5.5, to see how the different versions handle a certain workload. Or you might run multiple instances of the latest MySQL version, each managing a different set of databases.

Whether or not you use distinct server binaries, each instance that you run must …

The MySQL server is a large multi-threaded program primarily written in the C++ programming language.  Unfortunately,  data races and deadlocks in concurrent C++ programs are common.  Fortunately, the Thread Sanitizer can be used to find data races and deadlocks.  MySQL 5.7 does not support the Thread Sanitizer, but is is easy to add to the MySQL configuration using a simple build procedure.  When MySQL 5.7 is built with the Thread Sanitizer and database …