mysql - 如何将 GROUP BY 与 HAVING 一起使用？

Question

我试图从我的数据库中选择所有访问过我网站的 ips，从这个月开始，至少相隔一天不止一次，但我的 sql 查询显示错误。我做错了什么？

SELECT ip,COUNT(ip) AS matches
FROM ipAll
WHERE DATE LIKE  '%-12-%'
HAVING matches > '1'
GROUP BY ip

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 ip

Answer 1

HAVING 在 GROUP BY 之后:

SELECT ip, COUNT(ip) AS matches
FROM ipAll
WHERE DATE LIKE  '%-12-%'
GROUP BY ip
HAVING matches > 1;

但是，您应该更像这样编写查询:

SELECT ip, COUNT(ip) AS matches
FROM ipAll
WHERE MONTH(DATE) = 12
GROUP BY ip
HAVING matches > 1;

不要在日期上使用 LIKE，因为日期会使用本地国际化设置(隐式地)转换为字符串。这些可能会改变并破坏代码。另外，不要在需要数字的地方使用字符串常量。