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Displaying posts with tag: query (reset)
MongoDB versus MySQL Document Store command comparisons I

Both MongoDB and the MySQL Document Store are JSON document stores.  The syntax differences in the two products are very interesting.  This long will be a comparison of how commands differ between these two products and may evolve into a 'cheat sheet' if there is demand.

I found an excellent Mongo tutorial Getting Started With MongoDB that I use as a framework to explore these two JSON document stores.
The DataI am using the primer-dataset.json file that MongoDB has been using for years  in their documentation, classes, and examples. MySQL has created the world_x data set based on the world database used for years in documentation, classes and examples.  The data set is a collection of JSON documents filled with restaurants around Manhattan.

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Catching Slow and Frequent Queries with ProxySQL

In this blog post,  I’ll look at how to catch slow and frequent queries with ProxySQL.

More and more people are using ProxySQL because it is a great tool and it can help DBAs a lot. But many people do not realize that it is more powerful than it looks. It has many features and possibilities. I am going to show you one of my favorite “tricks” / use cases.

There are plenty of blog posts explaining how ProxySQL works. I am not going to that again. Instead, let’s jump straight to the point. There is a table in ProxySQL called “stats.stats_mysql_query_digest”. It is one of my favorite tables because it basically records all the queries that were running against ProxySQL. Without collecting any queries on the MySQL server, I can find …

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Common Table Expressions (CTEs) Part 1

Occasionally at conference or a Meetup, someone will approach me and ask me for help with a MySQL problem.  Eight out of ten times their difficulty includes a sub query. "I get an error message about a corrugated or conflabugated sub query or some such,"  they say, desperate for help.  Usually with a bit of fumbling we can get their problem solved.  The problem is not a lack of knowledge for either of us but that sub queries are often hard to write. 

MySQL 8 will be the first version of the most popular database on the web with Common Table Expressions or CTEs.  CTEs are a way to create temporary tables and then use that temporary table for queries. Think of them as easy to write sub queries!

WITH is The Magic WordThe new CTE magic is indicated with the WITH clause.

mysql> WITH myfirstCTE 
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Percona Live Featured Tutorial with Øystein Grøvlen — How to Analyze and Tune MySQL Queries for Better Performance

Welcome to another post in the series of Percona Live featured tutorial speakers blogs! In these blogs, we’ll highlight some of the tutorial speakers that will be at this year’s Percona Live conference. We’ll also discuss how these tutorials can help you improve your database environment. Make sure to read to the end to get a special Percona Live 2017 registration bonus!

In this Percona Live featured tutorial, we’ll meet Øystein Grøvlen, Senior Principal Software Engineer at Oracle. His tutorial is on How to Analyze and Tune MySQL Queries for Better Performance. SQL query …

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Personal Summary of the Percona Live Amsterdam 2015 Conference

Last week, 21-23 September, it took place the European MySQL Conference, or “Data performance Conference” as this year’s subtitle was “MySQL. NoSQL. Data in the cloud.”. This year, it changed its location from London to Amsterdam and, as most people I talked to agreed, the change was for good. As every year, Percona was the company organizing it, but it had the participation of all the major players in the open source MySQL/MongoDB/Cloud data world. Special mention goes to, which had more …

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What Makes the MySQL Audit Plugin API Special?

Why Should I Be Reading This?

To better understand how the MySQL Server functions, how to monitor the relevant server events, and find out what’s new in MySQL 5.7.8.

What’s Special About the Audit Plugin API?

Picking the right API for your new plugin is probably the most important design decision a plugin author will need to make.…

Log Buffer #426: A Carnival of the Vanities for DBAs

This Log Buffer edition transcends beyond ordinary and loop in few of the very good blog posts from Oracle, SQL Server and MySQL.


  • Variable selection also known as feature or attribute selection is an important technique for data mining and predictive analytics.
  • The Oracle Utilities SDK V4. has been released and is available from My Oracle Support for download.
  • This article provides a high level list of the new features that exist in HFM and details the changes/differences between HFM and previous releases.
  • In recent …
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Tracking MySQL query history in long running transactions

Long running transactions can be problematic for OLTP workloads, particularly where we would expect most to be completed in less than a second. In some cases a transaction staying open just a few seconds can cause behaviour that is entirely unexpected, with the developers at a loss as to why a transaction remained open. There are a number of ways to find long running transactions, luckily versions of MySQL from 5.6 onwards provide some very insightful instrumentation.

Here we will use the information_schema coupled with the …

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How to execute mysql query from a file in your mysql client terminal?

Being a terminal fan myself, I usually find myself running queries in the mysql client instead of a UI interface as it is much faster. You get to see the results instantaneously.

One thing which is pretty tedious is editing a big query again after once running it as the whole multi-line formatted query now appears on a single line, thus reducing its readability.

But no problems, you can edit your query from a file and run the file from your mysql client terminal as many times as you want with as many edits.

To do so, follow the below steps:

1. Open your terminal and cd into the folder you want to store our sample mysql file. Then save your query in a sample file called my_query.sql

$ cd /path/to/folder
$ vim my_query.sql

Save a sample query like:

SELECT * FROM employees

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MySQL Query Patterns, Optimized – Webinar questions followup

On Friday I gave a presentation on “MySQL Query Patterns, Optimized” for Percona MySQL Webinars.  If you missed it, you can still register to view the recording and my slides.

Thanks to everyone who attended, and especially to folks who asked the great questions.  I answered as many as we had time for  during the session, but here are all the questions with my complete answers:

Q: Can you compare the use of subqueries/multiple joins vs. multiple queries (e.g. temp tables)?

For performance, it’s hard to make …

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