What types of Referential Integrity constraint can be coded to maintain consistency between the rows of two tables:

Question

BlackTom AI · Accepted Answer

Let's break down the question and each option to understand referential integrity constraints that keep two tables in sync.
Option 1: Waterfall. This term is not a standard referential integrity action in relational databases. It sounds like a metaphor rather than a defined constraint, so it does not describe a valid mechanism to enforce consistency between related rows.
Option 2: Restrict. This is a recognized referential action. When you set a foreign key constraint to RESTRICT, the database prevents the operation that would create a violation, such as deleting a parent row or updating a key that has dependent child rows. This directly maintains consistency between the related tables by disallowing actions that would break the link.
Option 3: Self Referencing. While self-referencing (or self-join/foreign key referencing the same table) is a valid design pattern to model hierarchical data, it is not itself a referential integrity action between two distinct tables. It describes how rows relate within a single table, not how integrity is enforced across two tables.
Option 4: Set-to-Nothing. This phrasing resembles a description of a referential action like SET NULL or SET DEFAULT, which are standard options in many RDBMSes. However, the exact term "Set-to-Nothing" is not a canonical, officially supported action. If interpreted as SET NULL, it does maintain referential integrity but under a specific rule; as written, "Set-to-Nothing" is not a standard label and thus is not the correct canonical answer in typical exam contexts.
In summary, among the given choices, Restrict is the standard, correctly named referential integrity constraint used to maintain consistency between related rows in two tables by preventing deletions or updates that would violate the relationship.

What types of Referential Integrity constraint can be coded to maintain consistency between the rows of two tables:单项选择题

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