Confused generated_key or generatedKey

I’m a bit confused about the use of the key generated when using the result attribute. For CF8 they are talking about generated_key and in this article I just read Adobe Cookbook they use generatedkey. Which one of the two is correct?

Note I use mySql database!

It seems that both methods are working (at least in my case). At first there were several ways of retrieving the id of a just inserted record, depending on which database was used. generated_key, as in the question, was related to mySql database, for SQL server it was identitycol etc. With CF9 they have overcome this, by returning the same value for every database by using: generatedkey