如果返回null，则忽略行sql

Question

我正在使用别名。
以下是我的查询。我想避免使用NULL计数器显示行。

SELECT activity_id, user_id,
(CASE WHEN activity_id = 1 OR activity_id = 2 THEN user_id END) AS counter 
FROM eventedge_ticket_activity

它给出了以下结果：

如何跳过包含计数器NULL的行？

Answer 1

未经测试，但下面应该有效。

SELECT activity_id, user_id, 
CASE activity_id WHEN 1 THEN user_id 
                 WHEN 2 THEN user_id
                 ELSE NULL
END AS counter 
FROM eventedge_ticket_activity 
WHERE counter IS NOT NULL

Answer 2

以下是成功运行的查询。

SELECT * FROM (SELECT activity_id, user_id, case when activity_id=1 then user_id when activity_id=2 then user_id end as counter FROM eventedge_ticket_activity) db where counter != 'NULL'

Answer 3

我感觉样本数据已经过度简化，所以我可能错了，但这看起来只是解析数据一次的相同查询。

SELECT activity_id, user_id, 
 user_id AS counter 
FROM eventedge_ticket_activity 
WHERE activity_id in(1,2)

顺便说一下，marmeladze提供的答案也应该与我在评论中提到的改变一致[/ p>