How do I define a Drupal variable using phpmyadmin?
The variables are stored as serialised PHP strings so adding one to the database manually might just be a pain. You can do it quite easily though, just follow these steps:


Download and install the Devel module
Navigate to http://mysite.com/devel/php
Put this code in the textfield:

variable_set('drupal_weight_select_max', 1000);

Press the 'Execute' button.


If you do want to do it directly in PHPMyAdmin you can get away with a running a single query: 

INSERT INTO variable (`name`, `value`) VALUES ('drupal_weight_select_max', 'i:1000;')
  ON DUPLICATE KEY UPDATE `name` = 'drupal_weight_select_max', `value` = 'i:1000;';


and then flushing your caches.