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Lesson 07: Advanced MySQL Querying

Notes/errata/updates for Chapter 7:
See the official book errata at http://tahaghoghi.com/LearningMySQL/errata.php – Chapter 7 includes pages 223 – 275.

Supplemental blog post – ORDER BY NULL – read the blog post and the comments!

GROUP BY and HAVING examples – Supplemental blog post. The example of HAVING in the text shows a use case where HAVING is the same function as WHERE. This blog posts shows examples of HAVING that you cannot do any other way.

In the section called “The GROUP BY clause”, on pages 231-232, the book says:
“you can count any column in a group, and you’ll get the same answer, so COUNT(artist_name) is the same as …

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Continuent Road Map: One year after restart… Where next?

You may know Continuent Tungsten for our highly advanced MySQL replication tool, Tungsten Replicator, and for our state-of-the-art MySQL clustering solution, Tungsten Clustering. Our solutions are used by leading SaaS vendors, e-commerce, financial services and telco customers.

But there are more, many more, Tungsten deployments out there. Tungsten Replicator can be used for real-time data

Percona Blog Poll: How Do You Currently Host Applications and Databases?

Percona latest blog poll asks how you currently host applications and databases. Select an option below, or leave a comment to clarify your deployment!

With the increased need for environments that respond more quickly to changing business demands, many enterprises are moving to the cloud and hosted deployments for applications and software in order to offload development and maintenance overhead to a third party. The database is no exception. Businesses are turning to using database as a service (DBaaS) to handle their data needs.

DBaaS provides some obvious benefits:

  • Offload physical infrastructure to another vendor. It is the responsibility of whoever is providing the DBaaS service to maintain the physical environment – including hardware, software and best …
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FOSDEM MySQL & Friends Devroom – Call for Papers ends December 1st !

Hi all,

The Fosdem MySQL & Friends devroom Committee is now completed and you can find it on http://www.mysqlandfriends.eu/committee/

As you can see some old friends are back in the Committee and we have also new names. As usual all big 3 MySQL distributions are present in the Committee and several Community Members are completing the list.

Back to the topic of this article, the CfP will end on December 1st to let us review the proposed talks, check with the speakers and prepare the schedule.

Don’t hesitate too long, please submit using https://penta.fosdem.org/submission/FOSDEM18/

Sakila greetings !

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Fun with Bugs #56 - On Some Public Bugs Fixed in MySQL 5.7.20

While MySQL 8.0.x hardly has much impact on my regular work, recent MySQL 5.7.20 release is something to check carefully. MySQL 5.7 is widely used in production, as a base for Percona Server 5.7, some features may be merged into MariaDB 10.x etc. So, here is my review of some community reported bugs that were fixed in recently released MySQL 5.7.20, based on the release notes.

Usually I start with InnoDB bug fixes, but in 5.7.20 several related fixes were made only to bugs reported internally. So, this time I have to start with partitioning:

  • Bug #86255 - First one to write about, and the bug report is …
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A crashing bug in MySQL: the CREATE TABLE of death (more fun with InnoDB Persistent Statistics)

I ended one of my last posts - Fun with InnoDB Persistent Statistics - with a cryptic sentence: there is more to say about this but I will stop here for now.  What I did not share at the time is the existence of a crashing bug somehow related to what I found.  But let's start with some context.

In Bug#86926, I found a way to put more than 64 characters in the field table_name of the

How to Choose the MySQL innodb_log_file_size

In this blog post, I’ll provide some guidance on how to choose the MySQL innodb_log_file_size.

Like many database management systems, MySQL uses logs to achieve data durability (when using the default InnoDB storage engine). This ensures that when a transaction is committed, data is not lost in the event of crash or power loss.

MySQL’s InnoDB storage engine uses a fixed size (circular) Redo log space. The size is controlled by innodb_log_file_size and innodb_log_files_in_group (default 2). You multiply those values and get the Redo log space that available to use. While technically it shouldn’t matter whether you change either the innodb_log_file_size or innodb_log_files_in_group variable to control the Redo space size, most people just work with the innodb_log_file_size and leave innodb_log_files_in_group alone.

Configuring …

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Webinar Thursday, October 19, 2017: What You Need to Get the Most Out of Indexes – Part 2

Join Percona’s Senior Architect, Matthew Boehm, as he presents What You Need to Get the Most Out of Indexes – Part 2 webinar on Thursday, October 19, 2017, at 11:00 am PDT / 2:00 pm EDT (UTC-7).

Register Now

Proper indexing is key to database performance. Finely tune your query writing and database performance with tips from the experts. MySQL offers a few different types of indexes and uses them in a variety of ways.

In this session you’ll learn:

  • How to use composite indexes
  • Other index usages besides lookup
  • How to find …
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MariaDB 5.5.58 and MariaDB Connector/ODBC 3.0.2 now available

The MariaDB project is pleased to announce the immediate availability of MariaDB 5.5.58, as well as the recent release of MariaDB Connector/ODBC 3.0.2. These are both stable (GA) releases. See the release notes and changelog for details. Download MariaDB 5.5.58 Release Notes Changelog What is MariaDB 5.5? MariaDB APT and YUM Repository Configuration Generator Download […]

The post MariaDB 5.5.58 and MariaDB Connector/ODBC 3.0.2 now available appeared first on MariaDB.org.

Top Slowest Queries and their Associated Tables in MySQL

The following query gets data from performance_schema in MySQL and attempts to regex the digest to the list of tables in the same schema.

 SELECT d.*,  
(SELECT group_concat(distinct TABLE_NAME) FROM information_schema.TABLES
WHERE table_schema = d.schema_name and d.digest_text regexp table_name) table_name
FROM performance_schema.events_statements_summary_by_digest d
WHERE d.DIGEST_TEXT regexp "^(SELECT|UPDATE|DELETE|REPLACE|INSERT|CREATE)"
and d.LAST_SEEN >= curdate() - interval 7 day
ORDER BY d.SUM_TIMER_WAIT DESC limit 10\G


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