Question

The following SQL statement contains which type of subquery? SELECT title FROM books WHERE EXISTS (SELECT isbn FROM orderitems WHERE books.isbn = orderitems.isbn); a. correlated b. inline view c. multiple-column d. uncorrelated

Answer 1

Answer:

(a) Correlated.

Explanation:

Correlated subquery :These sub queries reference columns from outer table or uses values from outer query.These sub queries are processed atleast once for every row processed.So because of this reason correlated sub queries can be slow.Since the query in the question also uses value from the outer query so it is a correlated query.