Generate random string using PHPmyadmin

Hi

Must say first I'm using joomla to make a site which means I am very rookie at programming

Im using PhPmyadmin and I need to have at users's table a field that generates and store a "UNIQUE" 20 digits random string for each register, just like user ID (autoincremental field) this one won't be part of the registration form but it will be generated and filled at and by DB.

I found on this forum something similar at:
http://www.sitepoint.com/forums/show...-random-string

with the following code

Code:

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INSERT INTO user_table (name, uid) VALUES('Some Body', MD5(UUID()));

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Question
1. Can this code be used on PhPmyadmin
2. How could I inserted it
3. Will it work for my need
4. In case it won't what can I do


Thanks