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| Question ID 8180 | Which alter command would you use to reinstate a disabled primary constraint?
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| Option A | ALTER TABLE ENABLE PRIMARY KEY(ID)
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| Option B | ALTER TABLE CARS ENABLE CONSTRAINT cars_id_pk.
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| Option C | ALTER TABLE CARS ENABLE PRIMARY KEY(id)CASCADE;
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| Option D | ALTER TABLE CARS ADD CONSTRAINT cards_id_pk PRIMARY KEY(id);
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| Correct Answer | B |
Explanation Explanation/Reference: Explanation: Answers B is correct because this statement will enable the PRIMARY KEY. Incorrect Answers: A: It's wrong syntax to enable the PRIMARY KEY. C: It's wrong syntax to enable the PRIMARY KEY. D: You don't need to add or recreate PRIMARY KEY, just enable it with ALTER TABLE ENABLE CONSTRAINT statement. Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 145-148 Chapter 4: Creating Other Database Objects in Oracle
| Question ID 8181 | You have decided to disable the primary key constraint on the empid column and the check constraint on the job column. What happens when you try to enable the constraint after the update is completed?
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| Option A | You need to recreate the constraints once they are disabled.
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| Option B | Any existing rows that do not conform with the constraints are automatically deleted.
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| Option C | Only the future values are verified to conform with the constraints having the existing values unchecked.
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| Option D | The indexes on both the columns with the primary key constraint and the check constraints are automatically recreated.
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| Option E | All the existing columns values are verified to conform with the constraints and an error message is narrated if any existing values is not conformed.
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| Correct Answer | E |
Explanation Explanation/Reference: Explanation: Answers E is correct because it will be error if any existing values (old and updated) will violate the PRIMARY KEY or the CHECK constraints. Incorrect Answers: A: You don't need to recreate constraints, just enable them with ALTER TABLE ENABLE CONSTRAINT statement. B: Constraint will not be enabled if any existing rows violate it, but these rows will not be deleted automatically, user must do this manually and than again enable constraints. C: ALL existing values will be verified, not only updated or inserted, for the constraints violation. D: The indexes will not be automatically recreated. Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 145-148 Chapter 4: Creating Other Database Objects in Oracle