Question: 1/50
Which statement best describes the difference between a PRIMARY KEY constraint and a UNIQUE constraint in Oracle Database?
A PRIMARY KEY allows NULL values, but a UNIQUE constraint does not.
A table can have multiple PRIMARY KEY constraints but only one UNIQUE constraint.
A PRIMARY KEY constraint implicitly enforces NOT NULL and uniqueness, while a UNIQUE constraint enforces uniqueness but can allow NULLs.
UNIQUE constraints can be referenced by foreign keys, but PRIMARY KEY constraints cannot.