Oracle Group Subset of Selection Columns

Question

I have a column called vs_tblRentals which has the following columns:

RENTALID    CUSTOMERID    BOXID    RENTALDATE       RETURNDATE

As well as a column called vs_tblBoxes which has the following columns

BOXID       MOVIEID       MEDIUMTYPECODE       DATEBOXRECEIVED

I am trying to create a query that retrieve how many times each value in the BoxID column of vs_tblBoxes appears in the BoxID column of vs_tblRentals, essentially telling me how many times each box has been rented. I can do this through the following command:

SELECT COUNT(vs_tblRentals.BoxID) AS RentalCount
FROM vs_tblRentals
LEFT JOIN vs_tblBoxes B ON vs_tblRentals.BoxID = B.BoxID
GROUP BY vs_tblRentals.BoxID;

However, I also want to display information along side this RentalCount that is NOT part of the group- ideally my output would look something like this:

BoxID    MovieID   MediumTypeCode   RentalCount 

I would also like to display all the records in vs_tblRentals for the Boxes that have been rented more than 5 times.

How is this supposed to be done in Oracle 12c?

EDIT:

The following code successfully gets the Rental Count for each BoxID:

SELECT COUNT(vs_tblRentals.BoxID) AS RentalCount, vs_tblRentals.BoxID
FROM vs_tblRentals
LEFT JOIN vs_tblBoxes B ON vs_tblRentals.BoxID = B.BoxID
GROUP BY vs_tblRentals.BoxID;

And outputs the following:

RENTALCOUNT BOXID
1           337
1           691
1           43
4           321
4           123
4           665
4           674

But I cannot get this to work while displaying other information about the BoxID alongside this.

Sample Data From vs_tblBoxes:

BOXID   MOVIEID  MEDIUMTYPECODE     DATEBOXRECEIVED 
257     702      BD                 22-Nov-1953 
258     708      VHS                16-Jul-1988 
259     708      DVD                16-Jul-1988 

Sample data from vs_tblRentals

RENTALID    CUSTOMERID  BOXID   RENTALDATE    RETURNDATE    
1           1           257     06-Apr-2018   22-Apr-2018   
2           1           257     22-Mar-2018   NULL
3           1           259     26-Feb-2018   16-Mar-2018

Answer 1

What you want is probably to left join the tables in the opposite order (make entries in vs_tblRentals optional instead of the other way around), add the extra columns to the select and GROUP BY them too.

SELECT B.BoxID, B.MovieID, B.DateBoxReceived, COUNT(R.BoxID) AS RentalCount
FROM vs_tblBoxes B 
LEFT JOIN vs_tblRentals R
  ON R.BoxID = B.BoxID
GROUP BY B.BoxID, B.MovieID, B.DateBoxReceived;

Using GROUP BY on Oracle (in contrast to for example MySQL) requires you specify your query more fully and either group on each column you want to extract or generate it using an aggregate function (such as MAX or COUNT )

Doing neither will render an error.

Answer 2

Instead of left join use right outer join to do so..

select b.boxId, count(*) as RentalCount from 
vs_tblRentals r right outer join vs_tblBoxes b
on b.boxId = r.boxId group by b.boxId;