Question 4 (2 points) How can referential integrity be violated? Select all that apply. A primary key is inserted. A row containing a primary key is deleted. A foreign key is updated. A row containing a foreign key is deleted. A primary key is updated. A row containing a foreign key is inserted.

Referential integrity ensures that foreign keys correctly reference existing primary keys in related tables. Violations occur when these rules are not upheld. Here's an analysis of each option: 1. **A primary key is inserted.** - **Does Not Violate**: Inserting a primary key adds a valid reference point and maintains integrity. 2. **A row containing a primary key is deleted.** - **Violates Integrity**: Deleting a primary key that is referenced by a foreign key in another table leaves orphaned references. 3. **A foreign key is updated.** - **Violates Integrity**: Updating a foreign key to a value that doesn't exist in the referenced primary key table breaks the relationship. 4. **A row containing a foreign key is deleted.** - **Does Not Violate**: Deleting a row with a foreign key removes the reference but doesn't affect referential integrity. 5. **A primary key is updated.** - **Violates Integrity**: Changing a primary key that is referenced by foreign keys can leave those foreign keys pointing to non-existent entries. 6. **A row containing a foreign key is inserted.** - **Violates Integrity**: Inserting a row with a foreign key that doesn't match any existing primary key breaks the referential link. **Therefore, the actions that can violate referential integrity are:** - **A row containing a primary key is deleted.** - **A foreign key is updated.** - **A primary key is updated.** - **A row containing a foreign key is inserted.** **Answer:** All except the first and fourth options. Specifically, options 2, 3, 5, and 6.