Just Java™ 2

Subquery Selections

Quite frequently you want to submit a further select on the result of a select. There are several ways to do that, one way being to nest a select statement inside another. A nested select statement is called a subquery.

Here is an example of a subquery:

SELECT Person.name FROM PersonWHERE   Person.lives_in IN ('England', 'USA')AND   Person.name NOT IN     ( SELECT ListensTo.person_name FROM ListensTo       WHERE          ListensTo.music_group_name = 'Beatles' );

The simplest way to understand subqueries is to look at them piece by piece, starting from the innermost nested one. In this case, the nested select statement is:

( SELECT ListensTo.name FROM ListensTo  WHERE     ListensTo.music_group_name = 'Beatles' );

A moment's ...