Which two statements are true regarding constraints? (Choose two.)
A. A constraint can be disabled even if the constraint column contains data
B. A constraint is enforced only for the INSERT operation on a table
C. A foreign key cannot contain NULL values
D. All constraints can be defined at the column level as well as the table level
E. A columns with the UNIQUE constraint can contain NULL values
Answer: AE
Which two statements are true about sequences created in a single instance database? (Choose two.)
A. CURRVAL is used to refer to the last sequence number that has been generated
B. DELETE <sequencename> would remove a sequence from the database
C. The numbers generated by a sequence can be used only for one table
D. When the MAXVALUE limit for a sequence is reached, you can increase the MAXVALUE limit by using the ALTER SEQUENCE statement
E. When a database instance shuts down abnormally, the sequence numbers that have been cached but not used would be available once again when the database instance is restarted
Answer: AD
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