Question

I want an sql query to return the following data:

DES_EVENT | DATE_EVENT | INSCRIBED_PARTICIPANTS

And my Tables are (other columns are hidden)

**EVENT**
ID
DES_EVENT
DATE_EVENT

**EVENT_ACCESS**
NAME
EVENT_ID

**PARTICIPANT**
EVENT_ID

NOTE: The table participant registers every event in which a participant is enrolled.

I want to know what events a given user organized and how many participants were enrolled.

I’ve tried to do the following query:

SELECT
e.des_event,
e.date
FROM
event e,
event_access ea
WHERE
ea.name = ?
AND
ea.event_id = e.id

with this query I can not get the number of participants. So I tried to do the following query:

SELECT
e.des_event,
e.date
FROM
event e,
event_access ea,
participant p
WHERE
ea.name = ?
AND
ea.event_id = e.id
AND 
p.event_id = ea.event_id

and the rows of each event are repeated for each participant enrolled on this event, but I want to get this numbers of replicates in another column in the result of the sql like I put on the top of the question.

If I use the count() function the oracle returns an error

(ORA-00937: not a single-group group function)

How can I get the correct results?

Answer 1

If I understand you, you want

SELECT e.des_event,
       e.date,
       count(*) num_participants
  FROM event e,
       event_access ea,
       participant p
 WHERE ea.name = ?
   AND ea.event_id = e.id
   AND p.event_id = ea.event_id
 GROUP BY e.ddes_event, e.date

If that is not what you want, can you post a bit of sample data and post the results that you are looking for? Describing the results like you’ve done is great but some concrete test cases may help clarify things.