1Z0-006 Relational Data Model 2 — Questions and Answers
Question 1: Which normal form eliminates partial dependencies on a composite primary key?
- First Normal Form (1NF)
- Second Normal Form (2NF) (Correct answer)
- Third Normal Form (3NF)
- Boyce-Codd Normal Form (BCNF)
Correct answer: Second Normal Form (2NF)
2NF removes partial dependencies, meaning every non-key attribute must depend on the entire composite primary key, not just part of it.
Question 2: A table has columns: OrderID, ProductID, ProductName, Quantity. OrderID+ProductID is the PK. ProductName depends only on ProductID. Which normal form is violated?
- 1NF
- 2NF (Correct answer)
- 3NF
- 4NF
Correct answer: 2NF
ProductName depends only on ProductID (part of the composite key), creating a partial dependency that violates 2NF.
Question 3: Which constraint ensures a column cannot contain duplicate values but can contain NULLs?
- PRIMARY KEY
- UNIQUE (Correct answer)
- NOT NULL
- CHECK
Correct answer: UNIQUE
A UNIQUE constraint prevents duplicate values but, unlike PRIMARY KEY, allows multiple NULL values in Oracle.
Question 4: In the relational model, what term describes the set of all allowed values for a column?
- Relation
- Tuple
- Domain (Correct answer)
- Cardinality
Correct answer: Domain
A domain defines the set of permissible values for an attribute, such as positive integers or valid date ranges.
Question 5: Which type of relationship requires a junction (bridge) table to be implemented in a relational database?
- One-to-one
- One-to-many
- Many-to-many (Correct answer)
- Self-referencing
Correct answer: Many-to-many
A many-to-many relationship cannot be directly represented in relational tables and requires a junction table containing foreign keys from both sides.
Question 6: What is the degree of a relation?
- The number of rows in the table
- The number of columns in the table (Correct answer)
- The number of primary key columns
- The number of foreign key references
Correct answer: The number of columns in the table
The degree of a relation refers to the number of attributes (columns) it contains.
Question 7: Which action does the ON DELETE CASCADE option perform when a parent row is deleted?
- Sets child foreign key values to NULL
- Prevents deletion if child rows exist
- Automatically deletes related child rows (Correct answer)
- Raises an error and rolls back
Correct answer: Automatically deletes related child rows
ON DELETE CASCADE automatically removes all child rows that reference the deleted parent row, maintaining referential integrity.
1Z0-006 Relational Data Model 2
Which normal form eliminates partial dependencies on a composite primary key?