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Displaying posts with tag: sql (reset)
MySQL DropIndexIfExists

In reply to a question about how to conditionally drop an index on a table in MySQL. It appears the syntax doesn’t exist. However, maybe it does and I missed it. If I did miss it, I’m sure somebody will let me know. However, I simply have a dropIndexIfExists stored procedure for this type of database maintenance.

Below is my dropIndexIfExists stored procedure:

-- Conditionally drop the procedure.
DROP PROCEDURE IF EXISTS dropIndexIfExists;

-- Change the default semicolon delimiter to write a PSM
-- (Persistent Stored Module) or stored procedure.
DELIMITER $$

-- Create the procedure.
CREATE PROCEDURE dropIndexIfExists
( pv_table_name  VARCHAR(64)
, pv_index_name  VARCHAR(64))
BEGIN

  /* Declare a local variable for the SQL statement. */
  DECLARE stmt VARCHAR(1024);

  /* Set a session variable with two parameter markers. */
  SET @SQL := CONCAT('ALTER TABLE ',pv_table_name,'DROP INDEX ',pv_index_name);

  /* Check if the constraint exists. …
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MySQL 8+ Catalog

I was working through some tutorials for my students and noticed that there was a change in how a WHERE clause must be written against the information_schema.table_constraints table. It might have been made in an earlier release, I actually hadn’t checked it since 2014 when I wrote this early post on capturing MySQL Foreign Keys.

You could use the following WHERE case insensitive clause:

WHERE    tc.constraint_type = 'foreign key'

Now, you must use a case sensitive WHERE clause:

WHERE    tc.constraint_type = 'FOREIGN KEY'

I’d love to know why but I can’t seem to find a note on the change. As always, I hope this helps those looking for an answer.

Use MySQL to generate MySQL for Admin tasks

I recently learned how to use MySQL to generate MySQL statements for several admin-type Data Definition Language (DDL) SQL queries I needed to execute on the server. For many DBA’s this is likely nothing new and in fact, is a well-used tool in their kit. However, I mostly focus on developer-related tasks, so it is a fresh-in-my-mind learning experience. Continue reading for more information…

Some backstory for context

I’ve recently been porting over an existing vanilla PHP application to CodeIgniter 4. One of the new features is bootstrapping all of the necessary MySQL CREATE TABLE statements dynamically based on information parsed from a .fxl file (which is close kin to a .xml file structure-wise).

Each CREATE TABLE statement is complete with FOREIGN KEY constraint clauses to ensure data integrity between linking …

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OpenLamp.tech Issue #2

Hey friends over the weekend (Friday actually) I’ve published another issue of my weekly newsletter, OpenLamp.tech. Continue reading for more information…

This issue is full of great curated reads as well as a specific question I’ve asked readers and the community. Looking for some suggestions on planned migrations for upgrades to my WordPress site.

The Newsletter for PHP and MySQL Developers

In this weeks newsletter, there’s information on:

Here’s the full issue for you to read. You can always subscribe (it’s free) and have the weekly issue of OpenLamp.tech delivered directly to your inbox. Just think, no more waiting for me to post it here each Monday.

Visit the sign-up form below to …

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Free Medium Series – CodeIgniter 4 CRUD with MySQL

Generally, most all web applications are going to follow the elements of CRUD: Create, Read, Update, and Delete. CodeIgniter 4 is a powerful PHP web development framework that provides a rapid development environment. The CodeIgniter 4 Models come enriched with built-in CRUD functionality, which is covered in this compilation of Medium posts…

Image by Dariusz Sankowski from Pixabay 

Disclaimer: I originally published these articles first over on …

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MySQL WITH Clause

When I went over my example of using the WITH clause to solve how to use a series of literal values in data sets, some students got it right away and some didn’t. The original post showed how to solve a problem where one value in the data set is returned in the SELECT-list and two values are used as the minimum and maximum values with a BETWEEN operator. It used three approaches with literal values:

  • A list of Python dictionaries that require you to filter the return set from the database through a range loop and if statement that mimics a SQL BETWEEN operator.
  • A WITH clause that accepts the literals as bind variables to filter the query results inside the query.
  • A table design that holds the literals values that an analyst might use for reporting.

It was the last example that required elaboration. I explained you might build a web form that uses a table, and the table could allow a …

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CSV – SQL Import/Export Compilation

CSV or SQL? SQL or CSV? How about together? Without a doubt, CSV’s are one of the most common and familiar data interchange formats. Importing and exporting CSV data into or out of an SQL database is a staple process in most every data workflow. I’ve written numerous blog posts on both importing and exporting CSV data in an SQL environment. In this post, I am including all of these specific posts (as of the time of writing) in one easy-to-read and centralized location…

Image by xresch from  …

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MySQL with CTEs

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 …
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How to Retrieve MySQL Last Insert ID in CodeIgniter 4

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…

Self-Promotion:

If you enjoy the content written here, by all means, share this blog and your favorite post(s) with others who may benefit from or like it as well. Since coffee is my favorite drink, you can even buy me one if you would like!

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 …

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MySQL Table DDL file with phpMyAdmin

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…

Self-Promotion:

If you enjoy the content written here, by all means, share this blog and your favorite post(s) with others who may benefit from or like it as well. Since coffee is my favorite drink, you can even buy me one if you would like!

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 …

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