Relational Data Model Flashcards

Which relational model concept states that every row in a table must be uniquely identifiable?

Answer: Entity integrity

Entity integrity requires that every table has a primary key and that no primary key column contains a NULL value.

A FOREIGN KEY constraint with ON DELETE SET NULL means that when a parent row is deleted:

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.

Third Normal Form (3NF) eliminates which type of dependency?

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.

In Oracle, which pseudocolumn uniquely identifies each row's physical location in the database?

Answer: ROWID

ROWID is a pseudocolumn that provides the unique physical address of each row, identifying its exact storage location.

Which relational operation returns only rows that appear in both of two query result sets?

Answer: INTERSECT

INTERSECT returns only the rows that are common to both result sets, eliminating rows that appear in only one.

A CHECK constraint on a SALARY column reads: SALARY > 0. What happens if you try to insert a row with SALARY = -500?

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.

Which term describes a candidate key that was NOT chosen as the primary key?

Answer: Alternate key

An alternate key is any candidate key that was not selected as the primary key but still uniquely identifies each row.