On 24 April 2016 at 08:36, Thomas Munro <thomas.munro@xxxxxxxxxxxxxxxx> wrote: > For example, say we want all students who have one or more exam today: > > SELECT s.student_id, s.name > FROM student s > WHERE EXISTS (SELECT 1 > FROM exam e > WHERE e.student_id = s.student_id > AND e.exam_date = CURRENT_DATE) To be fair to SQL a far simpler version would be SELECT DISTINCT student_id, name FROM student INNER JOIN exam USING(student_id) WHERE exam_date=CURRENT_DATE; To find students with no exam today (the other point of your argument): SELECT student_id, name FROM student LEFT JOIN exam USING(student_id) WHERE exam_date=CURRENT_DATE AND exam.student_id IS NULL; Not really sure what the issue is with either of those. Once learned, they're both very easy and straightforward. Geoff -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
