Question

select distinct constraint_type from user_constraints;  C - C P R U 

Seems P means primary key and R means foreign key, correct? What are U and C?

Answer 1

Code Description                Acts On Level --------------------------------------------- C    Check on a table           Column O    Read Only on a view        Object P    Primary Key                Object R    Referential (Foreign Key)  Column U    Unique Key                 Column V    Check Option on a view     Object