Oracle Database SQL 12c 1z0-071 Exam Practice Test 4

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Question : 17 of 57

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Which three statements are true about defining relations between tables in a relational database? (Choose three.)

Primary key columns allow null values.
Every primary or unique key value must refer to a matching foreign key value.
Foreign key columns allow null values.
Every foreign key value must refer to a matching primary or unique key value.
Unique key columns allow null values.

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