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?

Question

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?

BlackTom AI · Accepted Answer

The question asks which constraint should enforce that the age in the Age column of the Students table lies between 18 and 30, inclusive.
Option 1: 'A DEF A U L T constraint to set the age to 18 if it is not within the range.' This describes an automatic modification (setting age to 18) rather than preventing invalid data, which is not how constraints are typically used. A default or trigger could enforce a value, but a CHECK constraint is needed to enforce a range, not a defaulting action. Therefore this option Misuses the constraint purpose and is incorrect.
Option 2: 'A CHECK constraint defined as ... (Age ≥ 18 AND Age ≤ 30)'. This matches the standard approach: a CHECK constraint validates that each row satisfies Age BETWEEN 18 AND 30, inclusive. The syntax (Age ≥ 18 AND Age ≤ 30) expresses the intended range check succinctly, so this option is the correct method to enforce the rule at the data level.
Option 3: 'A NOT NULL constraint to prevent null values in the Age column.' While NOT NULL ensures a value exists, it does not restrict the value to the range 18–30. An age of 17 or 40 would still be allowed, provided the field is not null. Hence this option does not fulfill the requirement and is incorrect.
Option 4: 'A UNIQUE constraint to ensure no two students have the same age.' A UNIQUE constraint would prevent duplicate ages across rows, which is unrelated to enforcing an age range and would unnecessarily constrain legitimate data if two students share the same age. This is incorrect for the stated goal.
In summary, only the CHECK constraint described in Option 2 properly enforces that Age lies between 18 and 30, inclusive, at the database level.

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?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?

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:

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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?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?

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?

Which of the following statements about creating constraints is incorrect?

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