There are two types of IFs in MySQL: the IF statement and the IF function. Both are different from each other. In this article, we will explain their diversities and show usage examples. Also, we will review other MySQL functions. Contents MySQL IF statements MySQL IF-THEN statement MySQL IF-THEN-ELSE statement MySQL IF-THEN-ELSEIF-ELSE statement Examples of […]
The post MySQL IF – Function and Statement (with Examples) appeared first on Devart Blog.
This is the second article of the series dedicated to MySQL trending.
As I wrote before, understanding your workload and seeing the evolution of it over time can help anticipating problems and work on solutions before the breakdown.
This article covers MySQL History List Length also known as HLL.
MySQL History List is related to InnoDB Undo Logs.
InnoDB is a multi-version storage engine (MVCC). It
keeps information about old versions of changed rows to support
transactional features such as concurrency and rollback. This
information is stored in undo tablespaces in a data structure
called a rollback segment.
This means that you can start a transaction and continue to see a consistent snapshot even if the data changed by other transaction. This behavior is related to the …
[Read more]I am currently working on a script to auto-enable parallel replication / multi-threaded replication (MTR) when there is replication lag. For testing this script, I need to trigger replication lag that would disappear after enabling MTR. I came-up with a simple solution for that, and I thought it could be useful to more people, so I am writing this blog post about it. Read-on for
MySQL Partitioned Tables
Learning Outcomes
Lesson Material
MySQL supports partitioning of tables. It supports range, list, hash, and key partitioning. Range partitioning lets you partition based on column values that fall within given ranges. List partitioning lets you partition based on columns matching one of a set of discrete values. Hash partitioning lets you partition based on the return value from a user-defined expression (the result from a stored SQL/PSM function). Key partitioning performs like hash partitioning, but it lets a user select one or more columns from the …
[Read more]The binary logging format in MySQL has been ROW by default since MySQL 5.7, yet there are still many users sticking with STATEMENT or MIXED formats for various reasons. In some cases, there is just simple hesitation from changing something that has worked for years on legacy applications. But in others, there may be serious blockers, most typically missing primary keys in badly designed schemas, which would lead to serious performance issues on the replicas.
As a Support Engineer, I can still see quite a few customers using STATEMENT or MIXED formats, even if they are already on MySQL 8.0. In many cases this is OK, but recently I had to deal with a pretty nasty case, where not using ROW format was found to cause the replicas to silently lose data updates, without raising any replication errors! Was it some really …
[Read more]Last week at Percona Live, I was asked what book I recommend for novices seeking to learn MySQL. For a long time, there has not been a good choice for modern versions of MySQL. Luckily I had just stumbled upon such a book. Now I am happy to recommend The MySQL Workshop – A practical guide to working with data and managing databases with MySQL by Petit and Cosentino.
The first chapter introduces database architectures, data types, storage engines (including MyRocks), and data normalization. The following chapter cover in great detail how to create a database, using MySQL Workbench, backups & restoring data, and creating indexes. Chapter four has a very good section on working with SQL, functions, and case statements. Then JOINs and stored procedures are covered.
In another book, that would probably be enough content, but later chapters plunge into using Node.JS, Access, and Excel with MySQL. …
[Read more]Codership is pleased to announce a new Generally Available (GA) release of the multi-master Galera Cluster for MySQL 5.7 and 8.0, consisting of MySQL-wsrep 5.7.37 (release notes, download) and MySQL-wsrep 8.0.28 (release notes, download) with Galera replication library 3.37 (release notes, download) implementing wsrep API …
[Read more]ADO.NET is a part of .NET Framework that provides access to different types of data sources. ADO.NET supports relational, XML and application data. ADO.NET resides in a layer between data sources and client applications and enables customers to retrieve, manipulate and update data through ADO.NET object model. ADO.NET architecture ADO.NET was introduced in the 10th […]
The post Introduction to ADO.NET appeared first on Devart Blog.
MySQL allows changing the location of the general log and the slow query log while the server is running by anybody having the SYSTEM_VARIABLES_ADMIN privilege to any location, including appending to existing files. In Percona Server for MySQL 8.0.28-19 we introduced a new system variable, secure-log-path, that can be used to restrict the location of these log files to avoid accidents or possible data corruption attacks.
When somebody with the system variables admin privilege changes these variables, the server runs a few sanity checks. Unfortunately, these checks are quite minimal, and only verify that the specified file is writable by mysqld.
Compared to this, other variables specifying write-related file and directory names are either read-only during the runtime of the server (such as datadir, tmpdir, or log_error), or have additional …
[Read more]This post covers filtering in the WHERE clause conditional using the MySQL BETWEEN operator. Continue reading this excerpt of premium MySQL content I’m creating for anyone to learn how to use MySQL…
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