Question

The following SQL statement contains which type of join?

SELECT title, order#, quantity
FROM books, FULL JOIN orderitems
ON books.isbn = orderitems.isbn;
A. equality
B. self-join
C. non-equality
D. outer join

Answer 1

The SQL statement provided appears to have a syntax error, but based on the intended operation, it represents a FULL JOIN, which is an outer join. So, the correct answer to the type of join in the SQL statement is D. outer join.

Step-by-step explanation:

The SQL statement mentioned in the question is attempting to perform a FULL JOIN between two tables, books and orderitems. However, the syntax of the SQL statement provided is incorrect as there is a comma that should not be present when using a JOIN clause. The correct usage of a FULL JOIN should not include a comma between the tables as it is a part of the JOIN syntax. The correct version of the query should resemble the following:

SELECT title, order#, quantity FROM books FULL JOIN orderitems ON books.isbn = orderitems.isbn;

Given the correct JOIN syntax, this statement is using a outer join, which is specifically a full outer join in this context. A full outer join returns all records when there is a match in either left or right table. The records that do not match from both sides will also appear in the result with NULL in the columns from the opposite side.

Using this concept, it completes the answer to the student's question, indicating that the correct answer is D. outer join.