1Z0-006 Relational Data Model 3 — Questions and Answers
Question 1: Which relational model concept states that every row in a table must be uniquely identifiable?
- Entity integrity (Correct answer)
- Referential integrity
- Domain integrity
- Column integrity
Correct answer: Entity integrity
Entity integrity requires that every table has a primary key and that no primary key column contains a NULL value.
Question 2: A FOREIGN KEY constraint with ON DELETE SET NULL means that when a parent row is deleted:
- Child rows are deleted automatically
- The deletion is prevented
- Child foreign key columns are set to NULL (Correct answer)
- Child rows are moved to an archive table
Correct answer: Child foreign key columns are set to NULL
ON DELETE SET NULL sets the foreign key column in child rows to NULL when the referenced parent row is deleted.
Question 3: Third Normal Form (3NF) eliminates which type of dependency?
- Partial dependencies
- Multi-valued dependencies
- Transitive dependencies (Correct answer)
- Join dependencies
Correct answer: Transitive dependencies
3NF removes transitive dependencies, where a non-key attribute depends on another non-key attribute rather than directly on the primary key.
Question 4: In Oracle, which pseudocolumn uniquely identifies each row's physical location in the database?
- ROWNUM
- ROWID (Correct answer)
- CURRVAL
- LEVEL
Correct answer: ROWID
ROWID is a pseudocolumn that provides the unique physical address of each row, identifying its exact storage location.
Question 5: Which relational operation returns only rows that appear in both of two query result sets?
- UNION
- INTERSECT (Correct answer)
- MINUS
- JOIN
Correct answer: INTERSECT
INTERSECT returns only the rows that are common to both result sets, eliminating rows that appear in only one.
Question 6: A CHECK constraint on a SALARY column reads: SALARY > 0. What happens if you try to insert a row with SALARY = -500?
- The row is inserted with SALARY set to NULL
- The row is inserted and the constraint is logged
- The insert fails with a constraint violation error (Correct answer)
- The SALARY value is automatically corrected to 0
Correct answer: The insert fails with a constraint violation error
A CHECK constraint violation causes the DML statement to fail with an ORA-02290 error and the row is not inserted.
Question 7: Which term describes a candidate key that was NOT chosen as the primary key?
- Foreign key
- Surrogate key
- Alternate key (Correct answer)
- Composite key
Correct answer: Alternate key
An alternate key is any candidate key that was not selected as the primary key but still uniquely identifies each row.
1Z0-006 Relational Data Model 3
Which relational model concept states that every row in a table must be uniquely identifiable?