Many of my students wanted to know how to write a simple PSM (Persistent Stored Module) for MySQL that saved the writes to all table as a group. So, to that end here’s simple example.

1. Create four sample tables in a re-runnable script file:

   /* Drop and create four tables. */
   DROP TABLE IF EXISTS one, two, three, four;
   CREATE TABLE one   ( id int primary key auto_increment, msg varchar(10));
   CREATE TABLE two   ( id int primary key auto_increment, msg varchar(10));
   CREATE TABLE three ( id int primary key auto_increment, msg varchar(10));
   CREATE TABLE four  ( id int primary key auto_increment, msg varchar(10));
   

2. Create a locking PSM across the four tables:

   /* Conditionally drop procedure. */
   DROP PROCEDURE IF EXISTS locking;
   
   /* Set delimiter to $$ to allow ; inside the procedure. */
   DELIMITER $$
   
   /* Create a transaction procedure. */
   CREATE PROCEDURE locking(IN pv_one   varchar(10)
                           ,IN pv_two …

Now that we’ve migrated to MySQL for our core database course, I’m building MySQL Workbench analysis problems. We start with a lecture trying to flush out a simple address, and then ask them to figure out how to link it to a customer table.

Designing it, I emphasized how it resolves the issue of a city occurring in multiple counties and states, like Fremont. Fremont occurs 17 times in the US and once in Haiti:

Naturally, I left two other design issues in the problem. I’m working through it for the first time with classes tomorrow. I hope it works well. Any comments?

The first tutorial supplementing the MySQL Connector/NET Developer Guide showed you how to connect and run static INSERT statement. It was a barebones PowerShell script with the MySQL Connector. This post shows you how to run a PowerShell script that uses a dynamic form to gather the MySQL credentials and then run a static query. Below is the MySQL Credentials form.

You enter the correct user name, password, hostname (or IP address), port, and database, like this:

Here’s the complete code for this staticQuery.ps1 PowerShell script:

# Add libraries for form components. …

It was interesting to note that the MySQL Connector/NET Developer Guide doesn’t have any instructions for connecting to the MySQL database from Microsoft Powershell. I thought it would be helpful to write a couple demonstrations scripts, especially when a quick search didn’t find a set of easy to follow samples.

The connection process to MySQL with Powershell is easiest with a non-query, so I created a db_connect table into which I could write a row of data:

CREATE TABLE db_connect
( db_connect_id  INT UNSIGNED PRIMARY KEY AUTO_INCREMENT
, version        VARCHAR(10)
, user           VARCHAR(24)
, db_name        VARCHAR(10));

The following insert.ps1 PowerShell script connects to the MySQL database, and inserts one row into the db_connect table:

# Connect to the libaray …

After downloading and installing MySQL 8.0.24 yesterday, I opened a command shell. In the command shell, I could access the MySQL Shell (mysqlsh.exe) but not the MySQL Client (mysql.exe). Typing in the following:

C:\WINDOWS\system32>mysql

It returned:

'mysql' is not recognized as an internal or external command,
operable program or batch file.

The MySQL Client (mysql.exe) was installed because MySQL Workbench relies on it. However, the MySQL Microsoft Software Installer (MSI) does not put the mysql.exe file’s directory in the common Windows %PATH% environment variable. You can find the required %PATH% directory variable by opening the File Manager and searching for the mysql.exe file.

You should return several directories and programs but the directory you want is:

C:\Program …

There are many ways to test and edit files. A lot of developers only use their favorite Integrated Developer Environment (IDE) but I find testing script files within the scope of a pipelined set of scripts much faster.

The ability to edit a script from within the MySQL Command-Line Interface (CLI) or MySQL Shell would be nice but unfortunately, doesn’t exist. You can always subshell to edit a file or list files in the present working directory, like:

mysql> \! vi task.sql

I prefer to test at the OS level while leveraging the up-arrow key for command history. Here’s my quick edit and test script technique from your present working directory:

1. Assume you create a task.sql test file, like:

   SELECT user() AS "Current User"\G
   

2. You can edit with vi or emac and test the script interactively from the present working directory.
   …

It’s a problem for my students who purchased the new Apple hardware that uses Apple Silicon because they can’t install a Docker MySQL instance. However, there is Homebrew formula that works on macOS Big Sur and the new Apple silicon. It supports:

• Intel Silicon: macOS Big Sur, Catalina, and Mojave
• Apple Silicon: macOS Big Sur

The Homebrew Formula does have conflicts that you may need to avoid. It is a solution for those with the new Apple silicon.

As always, I hope this helps those looking for a solution.

The idea of ACID transactions are a basic feature of SQL’s individual Data Manipulation Language (DML) commands, like the INSERT, UPDATE, and DELETE statements. Transactions across two or more tables are a natural extension of ACID compliance features provided by DML commands. However, they require a structured programming approach, like a store procedure or like API implemented in an imperative language.

Surprisingly, transaction management wasn’t covered well in Alan Beaulieu’s Learning SQL because he only provided pseudo code logic. While I thought troubleshoot some broken MySQL SQL/PSM logic would be a good learning experience for students, it wasn’t. So, I wrote this sample code to show how to achieve an all or nothing transaction across four tables.

The code for this example on transaction management lets you perform the important tasks necessary to effect transaction …

Somebody asked me about how they could convert an XML file to a CSV file to upload into MySQL. They were asking the question based on an old Convert XML to CSV blog post from 2008. Amazing though that is, I had to explain the process no longer requires manual tasks, like calling Java files from the Apache XML Project. All they needed to do was use the Oxygen XML Editor, which is why I wrote this blog post.

For example, I had them use the same sample XML file from the old blog post (shown below) with one change. The encoding value needs to change from latin1 (ISO-8859-1) to unicode (UTF-8). Then, they should put it into a local Windows directory (mine went into the …

Some believe the most important part of SQL is the ability to query data. Queries typically retrieve data by joining many tables together into useful result sets. This tutorial takes the position that visibility into the data helps those new to SQL understand how joins work. To that end, the queries use Common Tabular Expressions (CTEs) instead of tables.

Default behavior of a JOIN without a qualifying descriptor is not simple because it may return:

• A CROSS JOIN (or Cartesian Product) when there is no ON or USING subclause, or
• An INNER JOIN when you use an ON or USING subclause.

The following query uses JOIN without a qualifier or an ON or USING subclause. It also uses two copies of the single CTE, which is more or less a derived table and the result of a subquery held in memory. This demonstrates the key …