If a constraint is violated during data entry:

Question

BlackTom AI · Accepted Answer

When data entry occurs, constraints are rules that must be satisfied for the insert to succeed. 
Option 1: 'The table will be automatically removed.' This is incorrect; constraints do not delete tables or remove schema as a consequence of a bad row. They simply prevent invalid data from being stored. 
Option 2: 'The record will not be inserted into the table.' This is the core behavior of constraint enforcement: if the new row would violate a constraint (such as NOT NULL, UNIQUE, CHECK, or a foreign key), the database rejects the insert and the row is not added. In a transactional context, this rejection typically raises an error and may trigger a rollback of the attempted operation. 
Option 3: 'We never know what might happen.' This vague statement ignores the well-defined, deterministic behavior of constraint checking; databases either accept or reject the insert based on the defined rules. 
Option 4: 'The specific column that violates the constraint will contain NULL.' This is not generally true. A constraint violation does not automatically populate the offending column with NULL; rather, the entire insert is usually rejected unless the constraint is defined in a way that allows partial success (which standard single-row inserts do not). In most classic constraint scenarios, the row is not inserted at all.

If a constraint is violated during data entry:单项选择题

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

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?

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:

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If a constraint is violated during data entry:单项选择题

类似问题

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

​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?

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?

Which of the following statements about creating constraints is incorrect?

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