A quoi servent les lettres dans la colonne constraint_type de la table Oracle user_contraints?

Question

select distinct constraint_type from user_constraints; 

C 
- 
C 
P 
R 
U 

Semble P signifie clé primaire et R signifie clé étrangère, correct? Qu'est-ce que U et 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 

Answer 2

De l'12cR1 documentation:

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