Question

Which of the following SQL statements is not valid?

A. SELECT b.isbn, p.name
FROM books b NATURAL JOIN publisher p;
B. SELECT isbn, name
FROM books b, publisher p
WHERE b.pubid = p.pubid;
C. SELECT isbn, name
FROM books b JOIN publisher p
ON b.pubid = p.pubid;
D. SELECT isbn, name
FROM books JOIN publisher
USING (pubid);
E. None- all of the above are valid SQL statements

Answer 1

All provided SQL statements are valid and demonstrate different methods for joining tables in SQL. Hence, the correct answer is E. None- all of the above are valid SQL statements.

Step-by-step explanation:

The student has asked which of the following SQL statements is not valid:

• A. SELECT b.isbn, p.name FROM books b NATURAL JOIN publisher p;
• B. SELECT isbn, name FROM books b, publisher p WHERE b.pubid = p.pubid;
• C. SELECT isbn, name FROM books b JOIN publisher p ON b.pubid = p.pubid;
• D. SELECT isbn, name FROM books JOIN publisher USING (pubid);
• E. None- all of the above are valid SQL statements.

All of these SQL statements are syntactically correct under standard SQL usage. They represent different ways to join tables:

• Statement A uses a NATURAL JOIN which implicitly joins the tables using columns with the same names.
• Statement B uses the old-style comma-separated table names in the FROM clause with a WHERE clause to specify the join condition.
• Statement C uses the modern JOIN syntax with an ON clause to specify the join condition.
• Statement D uses the JOIN ... USING syntax, which is a shorthand for a join with an equality check on the specified column name in both tables.

Therefore, the correct answer is E. None- all of the above are valid SQL statements.