MySQL Archives - Belchamber Web Tools, AI Guidance & Code

MySQL: Exclude ‘group by’ group if field A in any row has value B with “Natural Join”

Aaron Belchamber — Sun, 21 Dec 2014 15:16:51 +0000

Querying databases get a little tricky when you have a stack of records associated with another table, perhaps a master table of accounts, and you’re trying to filter out values that would exclude the results from another group of results.In this example below, we are getting a list of organization IDs for all countries who […]

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Finding missing records of the right joined table in MySQL

Aaron Belchamber — Thu, 16 Oct 2014 10:23:36 +0000

Let’s say you have two database tables that are supposed to have the same record IDs. Perhaps they contain different data but share the same ID — for this example, we call it “user_id”. This query will select only the missing records of the right joined table. SELECT a.user_id, a.other_detail, b.user_id FROM tablea a LEFT […]

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Copying MySQL databases at the command line is fast and easy

Aaron Belchamber — Fri, 12 Sep 2014 11:59:23 +0000

Copying your MySQL databases from the command line, if you have privileges is easy, a lot easier than going into PHP MyAdmin and hoping the “Copy Database” function is available and it doesn’t time out… Here’s how you can copy databases to a remote server: mysqldump your_db_name | ssh host2 "mysql your_db_copy" Here how you […]

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PHP Developers: MySQLi & PDO forcing errors helpful for debugging queries when accessing private or protected isolated classes

Aaron Belchamber — Tue, 02 Sep 2014 11:37:17 +0000

Sometimes you don’t have much control over other people’s code but your code must interact with it. That’s one of the issues you will encounter when you work in a collaborative coding environment and you’re all developing code the proper way — there’s encapsulation so you know your code is isolated to only what you […]

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Mysql PDO standard insert (persist) of data to a table with placeholders to protect from MySQL injection attacks

Aaron Belchamber — Wed, 02 Jul 2014 18:52:29 +0000

This is a much more secure way to insert records and prevent MySQL injection. This assumes that $this-conn is your MySQLi PDO database connection object that you’ve already initialized:

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Quickly update a database field in MySQL by replacing one value with another with find and replace.

Aaron Belchamber — Fri, 21 Mar 2014 01:22:33 +0000

This is a MySQL query I find myself using in a bunch of situations when there are multiple users contributing to articles or other means of providing content. It’s usually to replace absolute links like “http://tools.belchamber.us/link-here/” to just “/link-here/”, but I found it’s useful for many other things. Recently, I had to import thousands of […]

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Quickly identify WordPress posts with duplicate content directly from the MySQL database with a single query

Aaron Belchamber — Sat, 15 Mar 2014 13:18:46 +0000

This handy query will return all the post IDs from all your WordPress posts that are exact duplicates. I usually run this query in a loop and then will delete the newest post duplicate. This problem usually comes from multiple users importing content into the new WordPress site or importing content from Joomla into WordPress […]

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Getting that strange “black diamond” and other weird symbol characters that return text from a database?

Aaron Belchamber — Sun, 02 Mar 2014 23:42:38 +0000

It’s inevitable, right when you thought your website was going smoothly, suddenly those strange symbols like the “black diamond question marks” start popping up. I sometimes have to clean variables returned from form input and other external text with PHP’s “iconv” function, but if the data is coming from a database and showing up funky, […]

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Connecting to PDO as an object

Aaron Belchamber — Wed, 26 Feb 2014 04:59:38 +0000

Moving from procedural with mysql_connect, etc to PDO objects should be an easy transition. It’s so much faster and reliable, too. The “mysql” library in PHP will soon be deprecated, so you hold-outs won’t have a choice. It’s actually less code to write and get whole queries into resulting arrays much faster. Trust me! Here’s […]

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