Co-Related Subqueries in TD

Example : SELECT Requests With a Correlated Subquery



The following SELECT request uses a correlated subquery to return the names of the employees who have the highest salary in each department.

SELECT name

FROM personnel p

WHERE salary = (SELECT MAX(salary)

FROM personnel sp

WHERE p.department=sp.department);

The following SELECT request uses a correlated subquery to return the names of publishers with no books in the library.

SELECT pubname

FROM publisher

WHERE 0 = (SELECT COUNT(*)

FROM book

WHERE book.pubnum=publisher.pubnum);