MySQL在具有IF条件的非唯一值上进行联接

Question

I have an attendees tables that looks like this:

event_id    user_id
  1           16
  1           12
  1           13
  2           14
  2           16
  2           12
  3           11
  3           16

and information about events in a table like this:

event_id    eventcenter_id      date_begin                date_end
    1             2         2016-10-31 18:00:00        2016-10-31 21:00:00
    2             1         2016-11-20 18:00:00        2016-11-20 18:40:00
    3             2         2016-11-20 15:00:00        2016-11-20 18:00:00

and finally a table that looks like this:

eventcenter_id              name
      1              Fire Hall
      2              Sunny Lake 

I need a query that returns all events being attended by a user. the result should return the event center name, date_begin and date_end sh i can use these objects in a calendar. When I try to join on the event_id from on the attendees table it gives the error not unique value on event_id. the result I'm after should look like this:

user_id eventCenter_name    date_begin                    date_end
   16        sunny lake    2016-10-31 18:00:00         2016-10-31 21:00:00
   16        fire hall     2016-11-20 18:00:00         2016-11-20 18:40:00
   16        sunny lake    2016-11-20 15:00:00         2016-11-20 18:00:00

Answer 1

Try this (maybe you have to change the name of the table eventcenter to the name you use):

SELECT aa.user_id, cc.eventCenter_name, bb.date_begin, bb.date_end
FROM attendees AS aa
INNER JOIN events AS bb
ON aa.event_id = bb.event_id
INNER JOIN eventcenter AS cc
ON bb.eventcenter_id = cc.eventcenter_id
ORDER BY aa.user_id ASC;

If you need for a specific user then use the following query:

SELECT aa.user_id, cc.eventCenter_name, bb.date_begin, bb.date_end
FROM attendees AS aa
INNER JOIN events AS bb
ON aa.event_id = bb.event_id
INNER JOIN eventcenter AS cc
ON bb.eventcenter_id = cc.eventcenter_id
WHERE aa.user_id = 16;