As an example for my class on the usefulness of Common Table Expressions (CTEs), I created three examples with Python. They extend an exercise in Chapter 9 on subqueries from Learning SQL by Alan Beaulieu. All of the examples work with the sakila sample database.

These bullets describe the examples:

1. Uses local variables and a range for loop and if statement that uses the variables to evaluate and add an element to the derived table (or query result set) from MySQL.
2. Uses a CTE with substitution variables from the Python program, which eliminates the need to evaluate and add an element to the query result set because the query does that.
3. Uses a table to hold the variables necessary to evaluate and add the element to the query result set.

This is the first Python program:

# Import the library.
import sys
import …

I use CodeIgniter 4 a great deal for learning, personal projects, and application development. In this post, I cover 2 different methods you can use and retrieve the MySQL Last Insert ID value after executing an INSERT statement in CodeIgniter. Continue reading for more information…

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Model Setup

Starting out, I use the CLI Generator feature and create a Model by executing this code in the terminal in the project root:

php spark make:model user --suffix

I have removed much of the …

If you need a structure only .sql file of a MySQL tables’ Data Definition Language (DDL), phpMyAdmin makes this super-easy with just a few clicks. Continue reading and learn how…

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Why use a DDL file?

Why would you need a structure-only .sql DDL file anyway?

Maybe you want to build out a tables’ structure on another server to bring in different data or something comparable, and want it void of any existing data.

Rather than creating the …

When the time comes that you no longer have a need for specific data, use DELETE to remove it completely from your table. CodeIgniter 4 Models have a delete() method that is super-easy to use. Continue reading for more information…

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CodeIgniter 4 CRUD Series with MySQL

I have written a now complete 4-part series over on my Medium account about CodeIgniter 4 Model CRUD operations. Feel free and visit any of the previous posts in the series to get up to speed:

• …

An interesting outcome of teaching SQL is discovering what skills new users require. One that I continuously rediscover is how to build a test case for various elements of SQL. This is a small article on querying with filters in the WHERE clause.

There are several of the exercises in Alan Beaulieu’s Learning SQL, 3rd Edition that would benefit from example setup. For example, Chapter 4 provides a snapshot of the payment table but doesn’t provide any instructions.

You can create an exercise_4_2 table with the following SQL statement if you plan to change the data:

CREATE TABLE exercise_4_2 AS
SELECT payment_id
,      customer_id
,      amount
,      payment_date
FROM   payment
WHERE  payment_id BETWEEN 101 AND 120;

Alternatively, you can create an exercise_4_2 view with the following SQL statement if you plan to only query the data:

CREATE VIEW exercise_4_2 AS
SELECT payment_id
, …

In some applications, data may never change. Yet, in others, data changes numerous times in its lifecycle. In SQL the UPDATE command changes existing rows of data. CodeIgniter 4 Models have 2 methods available for update operations: update() and save(). Continue reading and learn more about update()…

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CodeIgniter 4 CRUD Series with MySQL

This post is a re-share of an article I originally published on my Medium account and is part 3 in the CodeIgniter 4 CRUD with MySQL series. Be sure and …

Storing data is but one part of many in application development. Once data is stored, interested parties will likely want to see it. This is the Read aspect of CRUD – reading (or viewing) the data. Continue reading and see examples using CodeIgniter 4 built-in Model methods…

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In part 1 of this series, CodeIgniter 4 CRUD with MySQL: Create, I used the Model insert() method to store new rows of data. Now that the data is present in the table, we want to see that data.

There are 2 built-in Model …

I’m studying and beginning to use CodeIgniter 4 in ‘real-world‘ projects and want to share what I learn, as I pick up on concepts of the framework. I’m posting a series of CRUD-related posts over on Medium and resharing them here for any readers who are interested…

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…

Sometimes life is too surreal. Like when somebody says, “How do you get title case in an Oracle database?” That’s when you know three things about the individual, while suppressing laughter. They’re not very experienced with SQL, likely lazy, and don’t read the documentation.

I had a little fun with somebody today by taking them down a small rat-hole. “Oh, gosh … ” I said, “… let’s write a function for that.” Here’s the joke function, like:

CREATE OR REPLACE
FUNCTION title_case
( string VARCHAR2 ) RETURN VARCHAR2 IS
BEGIN
  /* Change upper case to title case. */
  RETURN UPPER(SUBSTR(string,1,1)) || LOWER(SUBSTR(string,2,LENGTH(string)));
END title_case;
/

Then, we tested it with a query from the pseudo dual table:

SELECT title_case('incredible') AS "Proper Name" FROM dual;

It returned:

Proper Name
----------
Incredible

Then, I said “Oh, that’s not his …

My students liked the MySQL Transaction post but wanted one that showed how an external web application would interact with MySQL in the scope of a transaction. So, I put a little PHP function together that write across two related tables in the context of a transaction. It uses mysqli (MySQL Improved Extension) to connect PHP to the MySQL database.

The function is barebones and uses the oldest approach of hidden inputs to maintain context between rendered forms using an HTML POST method. The hidden inputs are preceded with “h_” and snake case is used for variable names.

The function only writes to two tables. It writes to the member table and when that completes successfully to the contact table. The function:

• Submits credentials from a file and raises an error when they don’t work.
• Initializes a …