mysql - 没有 JOIN 的 SQL 查询

Question

我有一张 table :-

id, event_type

0, sent
1, sent
2, sent
3, sent
4, sent
2, delivered
4, delivered

现在，我想要所有那些id，其中有sent event_type，但没有delivered，即0, 1 , 3,

我可以使用嵌套查询或 MINUS 查询来完成此操作:-

select id from table where event_type = 'sent'
MINUS
select id from table where event_type = 'delivered';

但这是两个不同的查询。如何仅通过 1 个查询即可完成此操作？

我知道有可能进行 JOIN 查询。是否也有可能不使用 JOIN 查询并仍然获得必要的输出？

Answer 1

您可以使用 HAVING 子句和 GROUP BY 进行基于条件聚合的过滤:

SELECT id 
FROM your_table_name 
/* consider only those id(s) which has either sent and/or delivered */
WHERE event_type IN ('sent', 'delivered')
GROUP BY id 
HAVING SUM(event_type = 'sent')  /*Consider id which has 'sent' */
       AND NOT SUM(event_type = 'delivered') /*Ignore id which has 'delivered' */

<小时/>

另一个选项是使用 Correlated Subquery with NOT EXISTS和DISTINCT:

SELECT DISTINCT t1.id 
FROM your_table_name AS t1
WHERE t1.event_type = 'sent' 
  AND NOT EXISTS (SELECT 1 FROM your_table_name AS t2 
                  WHERE t2.id = t1.id AND 
                        t2.event_type = 'delivered')