[cwbriscoe]

You can but new rows will not be clustered until you re-cluster.

CLUSTER table_name USING index_name;

[sroussey]

I remember that for MySQL MyISAM (syntax was different) in the olden days. I thought Oracle let you do it though. My bad.

MySQL Innodb and other have real clustered primary key indexes with all the pluses and minuses that entails.