SQL SELECT 仅当所有项目匹配时

Question

So I have 2 tables:

Courses:
-course_ID (primary key)
-course_code
-title

Sections:
-section_ID (primary key)
-course_ID (foreign key)
-day

Each course has a number of sections that belong to it. Let's use an example.

The tables:

course_ID    course_code    title
1            ABC            Title1
2            BBC            Title2 

section_ID    course_ID    day
1             1            Monday
2             1            Tuesday
3             2            Monday
4             2            Monday

I want to be able to run a query that asks for all courses that give me ONLY the ones where all of their sections fit a certain criteria. So in this case, let's say I want to see "All the courses which have ALL of their sections on Monday". The desired output would be:

course_ID    course_code    title    section_ID    day
2            BBC            Title2   3             Monday
2            BBC            Title2   4             Monday

Notice how the entry (2, ABC, Title1, 1, Monday) is omitted? I can't seem to think of a way to do this. Thanks in advance!

Answer 1

Try this:

SELECT  *
  FROM courses c1
WHERE NOT EXISTS
(
    SELECT 1
      FROM  sections c2
      WHERE c1.course_id = c2.course_id
       AND  c2.day <> 'Monday' 
)

Answer 2

SELECT * FROM Courses WHERE course_ID NOT IN (SELECT DISTINCT course_ID FROM Sections WHERE day != 'Monday') 

Answer 3

Perhaps select courses where not exists (all sections except the sections that satisfy your criteria)?

Answer 4

SELECT c.*
FROM Courses c
WHERE NOT EXISTS (SELECT NULL FROM 
                  Sections s
                  WHERE Day <> Monday
                  and s.CourseID = c.CourseID)

Answer 5

select * from Sections s1 
   where not exists (
       select 1 from Sections s2 
           where s1.course_ID = s2.course_ID and s1.day <> s2.day)

It's saying to pull all sections where a record under the same course doesn't have a different day. That means you get single records as well as multiple records, so long as the days are the same.

Answer 6

You should select all the sections with day = 'Monday' and from that result, it's easy to join with the Courses table to get the courses.

select distinct c.course_id
    from Courses c
        inner join Sections s on s.course_id = c.course_id
    where s.day = 'Monday';