Have you considered an inner and outer join to the courses_times table? select distinct courses.* from courses inner join course_times monday_courses on courses.id = monday_courses.course_id and monday_courses.time_id = 1 left outer join course_times non_monday_courses on courses.id = non_monday_courses.course_id and non_monday_courses.time_id <> 1 where non_monday_courses.id is null
On Jan 5, 12:38 pm, Fernando Leandro <[email protected]> wrote: > Hello guys, > > I have a problem with how to do a sql query. > > I have 3 tables: courses, times and courses_times > > So for example, if i have the following data: > > Courses courses_times Times > id | name course_id | time_id id | day > > 1 | Math 1 | 1 1 | > Monday > 2 | Chimestry 1 | 2 2 | > Wednesday > 3 | History 1 | 3 3 | > Friday > 4 | Geografy 2 | 1 > 2 | 2 > 3 | 1 > > So, now, i want to make a query that returns to me only the courses that are > ministred on Monday, > but just ONLY Monday. For example, if a course is ministred Monday and > Wednesday i dont want. > In this example, i would like that my query returns just History, because is > the only course > that is just on Monday. > > SELECT courses.* > FROM courses > INNER JOIN courses_times ON courses_times.course_id = courses.id > INNER JOIN times ON courses_times.time_id = times.id > AND times.day = 'Monday' > > When i use a query like above, for example, it returns to me all the courses > that have association with Monday, > it returns Math, Chimestry and History, and i would like to receive just > History > > I know that this question is not about rails but i need to solve this > problem to continue my rails app, > and i would appreciate if someone could help me.. > > Does anyone have a solution for this? > > Thanks a lot > > Fernando -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
