Oracle user_constraintsテーブルのconstraint_type列の文字コードは何を表していますか？

Question

select distinct constraint_type from user_constraints;

C
-
C
P
R
U

Pは主キーを意味し、Rは外部キーを意味すると思われますか？ UとCとは何ですか？

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

Answer 2

12cR1ドキュメント から：

C - Check constraint on a table  
P - Primary key  
U - Unique key  
R - Referential integrity  
V - With check option, on a view  
O - With read only, on a view  
H - Hash expression  
F - Constraint that involves a REF column  
S - Supplemental logging