'strftime'不是公认的内置函数名称

Question

我正在使用Microsoft SQL Database Management Studio，它将不允许我使用strftime（）函数来运行查询。我必须按月创建一个表，每个月都有新用户和退订用户。

这基本上就是造成错误的原因：

SELECT strftime('%m', createddate) AS 'Month', COUNT(createddate) AS 'Subscribers',
       COUNT(dateunsubscribed) AS 'UNsubscribers'
FROM subscriber
GROUP BY 1
ORDER BY 1;

在没有strftime()的情况下如何运行此查询，或者如何使strftime()正常工作？

Answer 1

strftime是mysql函数，在Microsoft的sql-server中不可用。

对于这个简单的用例（从日期中提取一个月），您可以使用month：

SELECT   MONTH(createddate) AS [Month], 
         COUNT(createddate) AS [Subscribers],
         COUNT(dateunsubscribed) AS [UNsubscribers]
FROM     subscriber
GROUP BY 1
ORDER BY 1;

编辑：
为了解决注释中的问题，group by子句不像order by子句那样使用序数。您需要指定要分组的表达式：

SELECT   MONTH(createddate) AS [Month], 
         COUNT(createddate) AS [Subscribers],
         COUNT(dateunsubscribed) AS [UNsubscribers]
FROM     subscriber
GROUP BY 1
ORDER BY MONTH(createddate);