Question

This is a SQL question involving a join giving me more than I want.

I have 2 tables, an events table and singers table

EVENTS
event_id
event_name
num_attendees
tickets_sold
tickets_promo
event_date
... many other fields

SINGERS
event_id
singer

I’m trying to get event statistics from the events table if ANY of a list of singers performed.

EVENTS:
event_id num_attendees tickets_sold
   1        15              2500
   2         5              1575

Singers at the event:
event_id  singer
   1      bob
   1      jane
   2      bob

I’m interested in the statistics of events that either bob or jane sang in:

SELECT count(e.event_id) as count_events, sum(num_attendees) as sum_attentees, 
       sum(tickets_sold) as sum_tickets_sold
  FROM `events` e
       INNER JOIN singers s ON s.event_id = e.event_id 
   AND s.singer IN ("bob", "jane")
 WHERE event_date ...

Gives me a wrong count and sums since the join will give me 2 records for event 1, and 1 record for event 2 and the count of events will be 3.

How should I write this SQL? Thanks.

Answer 1

SELECT count(e.event_id) as count_events,
       sum(num_attendees) as sum_attentees,
       sum(tickets_sold) as sum_tickets_sold 
FROM events e 
WHERE e.event_id IN 
     (SELECT DISTINCT event_id FROM singers WHERE singer IN ("bob", "jane"));