I’ve been using Alan Beaulieu’s Learning SQL to teach my SQL Development class with MySQL 8. It’s a great book overall but Chapter 12 lacks a complete exercise. Here’s all that the author provides to the reader. This is inadequate for most readers to work with to solve the concept of a transaction.

Exercise 12-1

Generate a unit of work to transfer $50 from account 123 to account 789. You will need to insert two rows into the transaction table and update two rows in the account table. Use the following table definitions/data:

                      Account:
account_id     avail_balance    last_activity_date
-----------    --------------   ------------------
       123               450    2019-07-10 20:53:27
       789               125    2019-06-22 15:18:35

                      Transaction:
txn_id    txn_date      account_id    txn_type_cd    amount
------    ----------    -------+--    -----------    ------
  1001 …

In 2021, I wrote a MySQL example for my class on the usefulness of Common Table Expressions (CTEs). When discussing the original post, I would comment on how you could extend the last example to build a parametric reporting table.

Somebody finally asked for a concrete example. So, this explains how to build a sample MySQL parametric query by leveraging a filter cross join and tests the parameter use with a Python script.

You can build this in any database you prefer but I used a studentdb database with the sakila sample database installed. I’ve granted privileges to both databases to the student user. The following SQL is required for the example:

-- Conditionally drop the levels table.
DROP TABLE IF EXISTS levels;
 
-- Create the levels list.
CREATE TABLE levels
( level_id       int unsigned primary key auto_increment
, …

We have in the past covered Installing Galera Cluster 4 with MySQL 8 on Ubuntu 18.04 and also Installing Galera 4 with MySQL 8 on Ubuntu 20.04, and it would seem appropriate to also cover Ubuntu 22.04 LTS (Jammy Jellyfish). We do have excellent documentation and we also have the ability for you to automate all of this via the GUI tool, Galera Manager.

Prerequisites

• All 3 nodes have to have Ubuntu 22.04 LTS installed. The current version at the time of this writing is Ubuntu 22.04.3 LTS.
• Firewall (if setup) needs to …

This post goes through installing and configuring Ruby and Ruby on Rails for MySQL. The first step requires updating the Ubuntu OS:

sudo apt-get update

Interestingly, I found that the man-db service had inadvertently stopped. It raised the following error:

E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem. 

You run this command to find the problem with the dpkg utility:

sudo dpkg --configure -a

It returned:

Setting up man-db (2.10.2-1) ...
Updating database of manual pages ...
man-db.service is a disabled or a static unit not running, not starting it.

The following command started the man-db service:

sudo systemctl start man-db.service

Next, you install the prerequisite packages with this command:

sudo apt-get install -y git-core zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev …

Galera Manager supports three modes for supporting your Percona XtraDB Clusters: deploying to either Amazon Web Services, deploying to your own on premises hosts, and also just monitoring your clusters. In this blog post, we will go thru houw you should deploying a 3-node Percona XtraDB Cluster via Galera Manager on Amazon Web Services Elastic Compute Cloud (AWS EC2). You will realise that this process happens with just a simple API key and instance selection, so effectively you can have a Galera Manager setup in under fifteen minutes!

On AWS EC2, it is worth noting that Galera Manager itself can be deployed on the free tier for testing purposes. However, in production environments, you might expect up to 100GB of logs on a monthly basis, so you should plan accordingly.

Obtain Galera Manager by …

The momentum around Galera Manager development has been amazing. You report bugs or feature requests, and we fix them!

The major reason to release this was to ensure that Galera Manager would accept the new signing keys of Galera Cluster (key ID: 8DA84635).

One will now also note that gm-installer reports a new version: gm-installer version 1.12.0 (linux/amd64). And when you install it, Galera Manager itself is now at version 1.8.3. One of the major fixes is that Ubuntu 22.04 support for self-provided hosts is now exposed in the UI. This fixes …

Configuring Perl to work with MySQL is straight forward. While Perl is installed generally, you may need to install the libdbd-mysql-perl library.

You install it as a sudoer user with this syntax:

sudo apt install -y libdbd-mysql-perl

Display detailed console log →

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  libmysqlclient21
The following NEW packages will be installed:
  libdbd-mysql-perl libmysqlclient21
0 upgraded, 2 newly installed, 0 to remove and 12 not upgraded.
Need to get 1,389 kB of archives.
After this operation, 7,143 kB of additional disk space will be used.
Get:1 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 libmysqlclient21 amd64 8.0.35-0ubuntu0.22.04.1 [1,301 kB]
Get:2 http://us.archive.ubuntu.com/ubuntu jammy-updates/universe amd64 libdbd-mysql-perl amd64 …

It’s always interesting when I build new instances. Ubuntu 22.0.4 was no different but I ran into an issue with installing Apache2 and eventually loading the mysqli module.

The Apache2 error was an issue with an unsupported module or hidden prerequisite. The MySQLi required an Apache reload after installation. Contrary to some erroneous posts the mysqli driver is supported on PHP 8.1.

Apache2 installation starts first and the mysqli module reload and verification script follows. On Ubuntu, you install Apache2 if you’re unaware of the hidden pre-requisite, otherwise install the pre-requisite first and avoid the error.

This is the command to install the apache2 module:

sudo apt-get install -y apache2

It generated the following error message:

apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/wsgi.load: Cannot load …

In Alan Beaulieu’s wonderful book Learning SQL: Generate, Manipulate, and Retrieve Data, he uses a SQL 1 to demonstrates a CROSS JOIN in MySQL counting from 1 to 100. My students always find it difficult to read because the subqueries take so much space it makes it difficult to see the process, for example he gives this SQL 1 solution:

SELECT ones.x + tens.x + 1 AS counter
FROM
 (SELECT 0 AS x UNION ALL
  SELECT 1 AS x UNION ALL
  SELECT 2 AS x UNION ALL
  SELECT 3 AS x UNION ALL
  SELECT 4 AS x UNION ALL
  SELECT 5 AS x UNION ALL
  SELECT 6 AS x UNION ALL
  SELECT 7 AS x UNION ALL
  SELECT 8 AS x UNION ALL
  SELECT 9 AS x ) ones CROSS JOIN
 (SELECT 0 AS x UNION ALL
  SELECT 10 AS x UNION ALL
  SELECT 20 AS x UNION ALL
  SELECT 30 AS x UNION ALL
  SELECT 40 AS x UNION ALL
  SELECT 50 AS x UNION ALL
  SELECT 60 AS x UNION ALL
  SELECT 70 AS x UNION ALL
  SELECT 80 AS x UNION ALL
  SELECT 90 AS x ) tens
ORDER BY counter;

While anybody with a …

Working with my students to create an Ubuntu virtual environment for Python development with the MySQL database. After completing the general provisioning covered in this older post, I’d recommend you create a python symbolic link before installing the MySQL-Python driver.

sudo ln -s /usr/bin/python3 /usr/bin/python

You install the Python development driver with the following:

sudo apt-get -y install python3-mysql.connector

Create a python_connect.py file to test your Python deployment’s ability to connect to the MySQL database:

#!/usr/bin/python

# Import the library.
import mysql.connector
from mysql.connector import errorcode
 
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student', password='student',
                                host='localhost', …