Question

我希望我的约会在一个月内出现2位数，但我似乎只能得到1.我已经在互联网上寻找解决方案，并发现一些似乎应该有效，但是不断获得1064错误代码。我刚刚开始学习SQL几天，所以我可能遇到了正确的答案，只是不知道在查询中的位置。

这就是我在mySQL工作台中连接数据库的方式：

要连接到MySQL服务器，请将客户端程序指向：

主持人：applepie.cx67wtelpwox.us-east-1.rds.amazonaws.com

用户名：public

port：3306

这是我的疑问：

SELECT 
    concat(year, '-', month) AS theDate,
    dest,
    sum(1) AS numFlights,
    sum(cancelled) AS numCancelled,
    ((sum(Cancelled) / sum(1))) AS perCancelled
FROM flights WHERE year = 2013
    AND dest = 'SFO'
GROUP BY month
ORDER BY perCancelled desc

这就是我得到的：

2013-7  SFO 15401   862 0.0560
2013-6  SFO 14768   503 0.0341
2013-8  SFO 15478   322 0.0208

这就是我想要的：

2013-07 SFO 15401   862 0.0560
2013-06 SFO 14768   503 0.0341
2013-08 SFO 15478   322 0.0208

Answer 1

您可以使用lpad为月构建2个字符长度的字符串

SELECT 
    concat(year, '-', lpad(month,  2,'0')) AS theDate,
    dest,
    sum(1) AS numFlights,
    sum(cancelled) AS numCancelled,
    ((sum(Cancelled) / sum(1))) AS perCancelled
FROM flights WHERE year = 2013
    AND dest = 'SFO'
GROUP BY month
ORDER BY perCancelled desc

将str_to_date转换为YYYY-MM并在SQL中保留2位数的月份格式

1 个答案: