Question

I have a table with two columns meetingID and caseID. The meetingIDs can be from one of three categories, so I use a subquery to select a particular one by returning only the meetingIDs from another table that match that category.

Once I have this list of meetingIDs I want to count how many of them have two caseIDs. I also need to exclude a few caseIDs from the count, but that’s irrelevant for now.

Here’s the code I have so far;

  SELECT COUNT( meetingID ) , meetingID
FROM case_meeting
WHERE meetingID
 IN (

SELECT DISTINCT a.meetingID
FROM case_meeting a
INNER JOIN meeting b ON a.meetingID = b.meetingID
WHERE b.categoryID =  '1'
)
GROUP BY meetingID
HAVING COUNT( caseID ) =2

The main problem I have is actually writing code that will successfully count the number of meetingIDs that have two caseIDs instead of returning a list of them.

at the moment the code is returning a list where the number of rows matches the figure i want and in each row is a ‘2’

Answer 1

If there is a UNIQUE constraint on (meetingID, caseID):

SELECT cm.meetingID
FROM case_meeting AS cm
  INNER JOIN meeting AS m 
    ON m.meetingID = cm.meetingID
WHERE m.categoryID = 1
GROUP BY cm.meetingID
HAVING COUNT(*) = 2 ;

If there isn’t, change the last line to:

HAVING COUNT(DISTINCT cm.caseID) = 2 ;