SELECT * FROM product t1 LEFT JOIN promo_product t2 ON t1.idProduct = t2.product_idProduct WHERE t2.idPromoProduct IS NULL […]
Category: MySQL
Removing MySQL from Ubuntu or Debian Linux
One of the easiest way to upgrade MySQL installation is by first backing up the existing database and removing all traces of MySQL from the system. sudo apt remove –purge mysql* sudo apt autoremove sudo apt autoclean sudo apt remove dbconfig-mysql […]
MySQL unique index with multiple columns
In MySQL, If you have an existing table and you wanted to have unique index across multiple columns. This is very useful in implementing unique constraints. Please checkout the code snippet below. ALTER TABLE `prefix_counter` ADD UNIQUE `unique_prefix_counter`(`prefix`, `year`); […]
Using MySQL TIMESTAMPDIFF to delete unverified user records
Building a public website with user registration and email verification is typical. It will require users to validate their email by clicking a unique generated URL link. Sometimes, user registration with pending verification will grow exponentially and needs an automated cleanup of records. In this example I created a simple MySQL stored procedure to delete […]