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

Question

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

BlackTom AI · Accepted Answer

Let's examine what a CHECK constraint does in a relational database context, and then evaluate each statement.
Option 1: It requires an associated index to function properly. In reality, a CHECK constraint does not require an index to operate. Indexes can improve performance for some constraint checks, but they are not a prerequisite for a CHECK constraint to enforce its rule. This makes the statement incorrect.
Option 2: It can be used to ensure that a column contains only unique values. Unique values are the domain of UNIQUE constraints (and, for a primary key, the PRIMARY KEY constraint). A CHECK constraint validates values against a condition, not uniqueness, so this option is false.
Option 3: It is applied at the table level only. CHECK constraints can be defined at the column level or at the table level. Saying they are applied only at the table level ignores the column-level usage and is therefore inaccurate.
Option 4: It can be used to validate data values for an entire row. This aligns with how a CHECK constraint operates: it enforces a condition across one or more columns for each row, ensuring that the row’s data satisfies the specified rule. While it may reference multiple columns, it does apply to row-level data validation, making this statement true.

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

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:

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

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?

Which of the following statements about creating constraints is incorrect?

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