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:

Question

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:

BlackTom AI · Accepted Answer

When evaluating which SQL statement is invalid in the given scenario, it helps to review what each statement is trying to do and what the table definitions imply.
Option 1: ALTER TABLE books

ADD CONSTRAINT books_isbn_pk;
This statement is malformed. It attempts to add a constraint but does not specify the type of constraint (PRIMARY KEY, UNIQUE, FOREIGN KEY, etc.) nor the column(s) to which it applies. In SQL, ADD CONSTRAINT must be followed by a constraint type and the target column(s) (e.g., PRIMARY KEY (isbn) or UNIQUE (isbn)). Because the syntax is incomplete, this will produce a syntax/definition error regardless of data or existing constraints.

Option 2: ALTER TABLE books

ADD CONSTRAINT books_pubid_fk FOREIGN KEY (pubid)

REFERENCES publisher (pubid);
This statement is valid under typical relational database rules, provided the BOOKS table has a column named pubid and the PUBLISHER table has a column pubid, which the diagram indicates. It creates a foreign key relationship from books.pubid to publisher.pubid. Since there are no data yet and no prior constraints, adding this foreign key should succeed if the referenced column exists and types are compatible.

Option 3: ALTER TABLE books

ADD CONSTRAINT books_isbn_pk PRIMARY KEY (isbn);
This statement is also valid if the BOOKS table contains an isbn column. It defines isbn as the primary key for the table, which is a common and legitimate constraint. Again, with no data and no existing conflicting constraints, this should execute successfully as long as the isbn column exists and there are no existing primary keys on isbn.

In summary, the only option that is invalid due to incorrect syntax is Option 1, which omits the essential details of the constraint being added. The other two statements are structurally correct given the typical table definitions implied by the diagram.

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: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?

If a constraint is violated during data entry:

Which of the following statements about creating constraints is incorrect?

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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: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?

If a constraint is violated during data entry:

Which of the following statements about creating constraints is incorrect?

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?