与来自 JOIN 的 WHERE 一起加入 [重复]

Question

我有多个表，其中包含一些客户端的数据。我想要实现的是输出某个客户在第一个月被计费的金额。

所以我运行类似于下面的代码：

SELECT company,clientid,COALESCE (signed.value,reactivated.value) as 'Activation' , Amount FROM `tblclients`
LEFT JOIN tblcustomfieldsvalues  as signed  ON tblclients.clientid = signed.relid and signed.fieldid = 5
LEFT JOIN tblcustomfieldsvalues  as reactivated ON tblclients.userid = reactivated.relid and reactivated.fieldid = 27
LEFT JOIN (
    SELECT clientid,sum(total) as Amount FROM tblinvoices  
    WHERE month(invoicedate)=month(Activation) Group by clientid) as f on tblclients.clientid = f.clientid 

我的问题是，当我进行最后一次连接时，它给出了一个错误：'where 子句'中的未知列'Activation'。 如果我将其切换为 current_date，则查询的其余部分将起作用。

知道如何进行这项工作吗？

稍后编辑：我可能过度简化了查询，我也有一个 COALESCE

Answer 1

你可以试试下面-

SELECT company,clientid,activated.value as Activation , Amount 
FROM `tblclients`LEFT JOIN tblcustomfieldsvalues as signed ON tblclients.clientid = signed.relid and signed.fieldid = 5
LEFT JOIN 
( SELECT clientid,sum(total) as Amount 
  FROM tblinvoices Group by clientid
) as f on tblclients.clientid = f.clientid and month(invoicedate)=month(Activation)