Oracle object

so,i have problem with: drop typei have 2 new Objects typ : Student ref Profand Prof ref Studentso how can i drop these Object?
[155 byte] By [cuongdeutsch2@yahoo.coma] at [2007-11-27 6:45:57]
# 1
Drop the constraints first.
dcmintera at 2007-7-12 18:18:16 > top of Java-index,Database Connectivity,Java Database Connectivity (JDBC)...
# 2
very good advice .thanks so much
cuongdeutsch2@yahoo.coma at 2007-7-12 18:18:16 > top of Java-index,Database Connectivity,Java Database Connectivity (JDBC)...
# 3
i have found ,that it works too with drop type objectname force;
cuongdeutsch2@yahoo.coma at 2007-7-12 18:18:16 > top of Java-index,Database Connectivity,Java Database Connectivity (JDBC)...