Question

Given the following query:

SELECT zip, order#
FROM customers NATURAL JOIN orders;
Which of the following queries is equivalent?
A. SELECT zip, order#
FROM customers JOIN orders
WHERE customers.customer# = orders.customer#;
B. SELECT zip, order#
FROM customers, orders
WHERE customers.customer# = orders.customer#;
C. SELECT zip, order#
FROM customers, orders
WHERE customers.customer# = orders.customer# (+);
D. None of the above

Answer 1

Queries A and B are both potentially equivalent to the natural join in the original query if 'customer#' is the matching column. Query C is incorrect as it indicates an outer join. The correct answer is 'None of the above' since the question implies there is only one correct answer, but here two are potentially correct.

Step-by-step explanation:

The student's question involves finding an equivalent SQL query to a natural join between the customers and orders tables. A natural join automatically matches columns with the same names in both tables and returns the result.

Given the original query: SELECT zip, order# FROM customers NATURAL JOIN orders; The equivalent query without using NATURAL JOIN would need to explicitly specify the condition on which the tables are joined. Both queries A and B in the question are equivalent to the original query, if customer# is indeed the matching column in both tables. However, query C is incorrect because the use of (+) indicates an outer join in Oracle SQL.

Therefore, the correct answer is D. None of the above, since queries A and B are both potentially correct, while the question asks for one equivalent query.