How to get a String randomly?

[Kidd y.Chen]

I just learned some basic knowledge about jsp&MySql, so I tried my best to do some practice. I designed a login system, and in my register_users table in database, there is one column which is String type, called ru_id, storing value to every register users, so the value in the column should be created automatically and can't not be the same in two of them.

So I want to know how randomly to get the only one String value, in restrict length, during registration in my this login system. Thank you.

[Bear Bibeault]

Moved to the JDBC forum.

[Bear Bibeault]

Does it have to be a string? Frequently, database sequences are used to generate unique numeric values for use as primary keys.

[Kidd y.Chen]

That's nice advice, I'll try by myself first, thank you!