Which two statements are true about the Key Exists validator? (Choose two.)
A.
It always issues a select to the database to ensure all data is up to date.
B.
It first checks the cache for match and then goes to the database only if necessary.
C.
It cannot validate any data changes that happened in the current transaction that have not yet been
committed to the database.
D.
It can validate any data changes that happened in the current transaction that have not yet been committed
to the database.
E.
It can be used only with attributes that are defined as primary keys in the database.
Explanation:
The “Key Exists” Validator is validator that can be defined at either the entity level or the attribute level but
pertains to an entity object attribute to check whether a key exists based on a primary key, foreign key or an
alternate key. The “Key Exists” validator will check first the cache querying rows not committed yet to the
database and if the key is not found in the cache will run a check in the database.
http://antonis-antoniou.blogspot.se/2014/07/using-adf-bc-declarative-built-in-rules.html