添加条件时，为什么此SQL查询会返回重复的结果？

Question

以下代码用于获取帮助台任务的计数，我正在尝试检索特定部门的计数。但是，它似乎无法正常工作，我不知道为什么会这样。 SQL查询如下：

SELECT 
    datepart(mm, m.creationdate) AS themonth, 
    datepart(yyyy, m.creationdate) AS theyear, 
    count(*) AS total, count(nullif(m.thetype, '1')) AS regular, 
    count(nullif(m.thetype, '2')) AS multi, 
    count(nullif(m.thetype, 11)) AS quick, 
    count(nullif(m.enteredby, 'WriteLog')) AS mn, 
    Count(case when m.thetype=10 then 1 else null end) as Errors, 
    Count(case when m.thetype=12 then 1 else null end) as FOH 
FROM mlist AS m 
INNER JOIN TypeList AS t ON t.typekey = m.thetype 
INNER JOIN Notes AS mn ON m.id = mn.id 
WHERE mn.enteredby in ('210','181','229','240','266','284','291','238','239','272','273') 
GROUP BY datepart(mm, m.creationdate), datepart(yyyy, m.creationdate) 
ORDER BY datepart(yyyy, m.creationdate) DESC, datepart(mm, m.creationdate) DESC 

我最近添加了部分：

WHERE mn.enteredby in ('210','181','229','240','266','284','291','238','239','272','273')

在许多情况下导致更高的计数，除非它们是重复的结果，否则没有任何意义。这里有明显的问题吗？