SQL 选择 : I need a "IN ALL" Clause

Question

我有两张 table 。我需要所有 organizer_id s 组织了 2010 年至 2012 年间的所有事件。

event
--------- 
event_id
name
year


event_organizer
---------
event_id
organizer_id

我试过这样的事情:

SELECT organizer_id 
  FROM event_organizer
 WHERE event_id IN (SELECT event_id 
                      FROM event 
                     WHERE year>=2010 AND year<=2012);

但它没有用，因为我只需要 organizer_id它组织了 2010 年和 2012 年之间的所有事件。我不知道查询应该如何像我想要的那样工作。

Answer 1

你可以写:

SELECT t1.organizer_id
  FROM ( SELECT eo.organizer_id,
                COUNT(1) AS num_events
           FROM event_organizer eo
           JOIN event e
             ON eo.event_id = e.event_id
          WHERE e.year BETWEEN 2010 AND 2012
          GROUP
             BY eo.organizer_id
       ) t1
  JOIN ( SELECT COUNT(1) AS num_events
           FROM event e
          WHERE e.year BETWEEN 2010 AND 2012
       ) t2
    ON t1.num_events = t2.num_events
;

(上面的想法是:对于每个组织者，找出他在 2010 年和 2012 年之间组织了多少事件。然后，将其与 2010 年和 2012 年之间的事件总数进行比较。如果这两个数字相同，然后组织者组织了该时间段内的所有事件。)

或者，您可以编写:

SELECT organizer_id
  FROM organizer       -- I assume you have an 'organizer' table?
 WHERE organizer_id NOT IN
        ( SELECT o.organizer_id
            FROM event e
           CROSS
            JOIN organizer o
            LEFT
           OUTER
            JOIN event_organizer eo
              ON e.event_id = eo.event_id
             AND o.organizer_id = eo.organizer_id
           WHERE e.year BETWEEN 2010 and 2012
             AND eo.event_id IS NULL
        )
;

(这个想法是:找到所有事件组织者配对，使得组织者没有组织事件。然后，返回所有没有出现在任何此类配对中的组织者。)