mysql - 查询有问题

Question

我有一个包含 user_id 和 last_updated 的数据库

SELECT user_id, MAX(last_updated) as timestamp 
  FROM online 
 WHERE user_id > 0 
 GROUP_BY user_id

我遇到了这个错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'GROUP_BY user_id' at line 1

SELECT user_id, MAX(last_updated) as timestamp 
  FROM online 
 WHERE user_id > 0 
 GROUP_BY user_id

有人建议我使用上面的查询，所以我不确定为什么会出现此错误

我用谷歌搜索了group_by，但没有发现我做错了什么。我想也许 as timestamp 但不确定!

Answer 1

它是 GROUP BY 而不是 GROUP_BY...

SELECT user_id, MAX(last_updated) as timestamp 
  FROM online 
 WHERE user_id > 0 
 GROUP BY user_id

更新

根据评论，还要注意 timestamp 是一个保留字。您应该使用别名(即 max_last_updated)或使用反引号将其转义(即 `timestamp`)