Question

我有两个关系表，person和event_registration，我想选择已注册10个或更少事件的所有人。我找到了一个似乎正确的查询。它可以通过以下查询找到这些人：

  SELECT person_id 
    FROM event_registration 
GROUP BY person_id 
  HAVING COUNT(*) <= 10

注意，event_registration.person_id与匹配person.id的表行相关。现在我想使用此查询搜索person表，但我的查询似乎崩溃了mysql。为什么呢？

SELECT id 
  FROM person 
 WHERE id IN (
       SELECT person_id 
         FROM event_registration 
     GROUP BY person_id 
       HAVING COUNT(*) <= 10
 )

我想更改查询的原因是因为我还查找其他属性，因此（更接近）最终查询将类似于：

SELECT * 
  FROM person 
 WHERE name LIKE '%something%' 
   AND AGE > 20 
   AND id IN (
       SELECT person_id 
         FROM event_registration 
     GROUP BY person_id 
       HAVING COUNT(*) <= 10
 )

当然这不起作用，因为mysql似乎崩溃了。我做错了什么？

Answer 1

SELECT distinct id FROM person 
WHERE id IN
    (SELECT person_id 
     FROM event_registration 
     GROUP BY person_id HAVING COUNT(*) <= 10)

mysql：选择具有一定数量关系行的人

1 个答案: