Relational Data Model Flashcards

Which normal form eliminates partial dependencies on a composite primary key?

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.

A table has columns: OrderID, ProductID, ProductName, Quantity. OrderID+ProductID is the PK. ProductName depends only on ProductID. Which normal form is violated?

Answer: 2NF

ProductName depends only on ProductID (part of the composite key), creating a partial dependency that violates 2NF.

Which constraint ensures a column cannot contain duplicate values but can contain NULLs?

Answer: UNIQUE

A UNIQUE constraint prevents duplicate values but, unlike PRIMARY KEY, allows multiple NULL values in Oracle.

In the relational model, what term describes the set of all allowed values for a column?

Answer: Domain

A domain defines the set of permissible values for an attribute, such as positive integers or valid date ranges.

Which type of relationship requires a junction (bridge) table to be implemented in a relational database?

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.

What is the degree of a relation?

Answer: The number of columns in the table

The degree of a relation refers to the number of attributes (columns) it contains.

Which action does the ON DELETE CASCADE option perform when a parent row is deleted?

Answer: Automatically deletes related child rows

ON DELETE CASCADE automatically removes all child rows that reference the deleted parent row, maintaining referential integrity.