Correlated subqueries in SELECT
Let’s say we want to display the
year of publishing of the oldest published book that belongs to each course, with the
name of the course itself.
There is one way of doing it using
However, there is another way of doing it, using a subquery in the
This explains that a subquery that can return either a single value, or a list of values, can also substitute a field or part of a field in
Notice that the filter in the subquery utilizes a column from the outer/parent query. So this, is also an example of a