Which of the following statements about the FOREIGN KEY constraint is incorrect?

Question

Which of the following statements about the FOREIGN KEY constraint is incorrect?​

BlackTom AI · Accepted Answer

Question restatement: Which of the following statements about the FOREIGN KEY constraint is incorrect?

Option 1: 'The constraint is added to (or defined in) the child table to ensure the referential integrity between the parent table and the child table.' This is a correct description. A foreign key is defined on the child (referencing) table and enforces that values in the foreign key column(s) correspond to existing values in the parent table, thus maintaining referential integrity.

Option 2: 'When the constraint exists, by default a record cannot be deleted from the parent table if matching entries exist in the child table.' This statement is also correct in many database systems. Unless you specify a cascading action (like ON DELETE CASCADE) or other options (like SET NULL, NO ACTION), deleting a parent row that has dependent child rows would be blocked or rejected to preserve referential integrity.

Option 3: 'When the keywords ON DELETE CASCADE are included in the constraint, the Foreign Key constraint will be dropped when you drop a Primary Key constraint of the parent table.' This is the incorrect statement. ON DELETE CASCADE defines behavior for what happens to child rows when a parent row is deleted, not what happens to the FK constraint itself when the parent’s primary key is dropped. Dropping a primary key typically affects the key’s existence and may require dropping or altering dependent foreign keys, but it does not entail automatically dropping the entire foreign key constraint simply because ON DELETE CASCADE was specified. The constraint’s existence and behavior are not tied to the act of dropping a primary key in this way.

Option 4: 'When the keywords ON DELETE CASCADE are included in the constraint, a corresponding child record will be automatically removed when the parent record is deleted.' This is a correct description of ON DELETE CASCADE. Deleting a parent row cascades the delete to all matching child rows, removing them automatically.

Summary of reasoning: Options 1, 2, and 4 accurately describe standard foreign key behavior in relational databases. Option 3 misstates the effect of ON DELETE CASCADE on the FK constraint itself when the parent table’s primary key is dropped, which is not how cascading delete semantics work. The incorrectness lies in conflating cascade delete behavior with automatic dropping of the constraint during a primary key drop.

Which of the following statements about the FOREIGN KEY constraint is incorrect?单项选择题

类似问题

Which of the following statements about creating constraints is incorrect?

The UNIQUE constraint differs from the PRIMARY KEY constraint in what way?

Which 𝐴 𝐿 𝑇 𝐸 𝑅 𝑇 𝐴 𝐵 𝐿 𝐸 statement would be used to remove the 𝐹 𝑂 𝑅 𝐸 𝐼 𝐺 𝑁 𝐾 𝐸 𝑌 constraint named 𝐹 𝐾 𝐸 𝑚 𝑝 𝐷 𝑒 𝑝 𝑡 from the 𝐸 𝑚 𝑝 𝑙 𝑜 𝑦 𝑒 𝑒 𝑠 table?

You have a 𝑆 𝑡 𝑢 𝑑 𝑒 𝑛 𝑡 𝑠 table with an 𝐴 ≥ column. You need to enforce a rule that the age must be between 18 and 30, inclusive. Which constraint should you use and how?

Which of the following statements about the 𝐶 𝐻 𝐸 𝐶 𝐾 constraint is true?

If a constraint is violated during data entry:

Which of the following statements about creating constraints is incorrect?

Which of the following SQL statements is invalid and will result in an error message? Assume that the BOOKS table currently has no constraints and contains no data. For your information, BOOKS and PUBLISHER tables have a relationship shown below:

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单

Which of the following statements about the FOREIGN KEY constraint is incorrect?​单项选择题

类似问题

​Which of the following statements about creating constraints is incorrect?​

The UNIQUE constraint differs from the PRIMARY KEY constraint in what way?​

Which 𝐴 𝐿 𝑇 𝐸 𝑅 𝑇 𝐴 𝐵 𝐿 𝐸 statement would be used to remove the 𝐹 𝑂 𝑅 𝐸 𝐼 𝐺 𝑁 𝐾 𝐸 𝑌 constraint named 𝐹 𝐾 𝐸 𝑚 𝑝 𝐷 𝑒 𝑝 𝑡 from the 𝐸 𝑚 𝑝 𝑙 𝑜 𝑦 𝑒 𝑒 𝑠 table?

You have a 𝑆 𝑡 𝑢 𝑑 𝑒 𝑛 𝑡 𝑠 table with an 𝐴 ≥ column. You need to enforce a rule that the age must be between 18 and 30, inclusive. Which constraint should you use and how?

Which of the following statements about the 𝐶 𝐻 𝐸 𝐶 𝐾 constraint is true?

If a constraint is violated during data entry:

Which of the following statements about creating constraints is incorrect?

Which of the following SQL statements is invalid and will result in an error message? Assume that the BOOKS table currently has no constraints and contains no data. For your information, BOOKS and PUBLISHER tables have a relationship shown below:

更多留学生实用工具

希望你的学习变得更简单

Which of the following statements about the FOREIGN KEY constraint is incorrect?单项选择题

Which of the following statements about creating constraints is incorrect?

The UNIQUE constraint differs from the PRIMARY KEY constraint in what way?