MySQL Query to insert random numbers into a column

Question

I've added a 'join_key' column into my 'providers' table as an update.

I need to fill the 'join_key' for all existing providers with random numbers/letters 10 characters in length.

Can anyone help me with the query to do it? The column is currently NULL.

I've tried this:

UPDATE `providers` SET `join_key` = 1000 * RAND() WHERE 1; 

but i keep getting a decimal point: 19.714112411918226