聚合函數或GROUP BY子句

Question

我用下面的查詢：

select Patients.LastName, 
    avg (PatientVisits.Pulse)as pulse, 
    avg (patientvisits.depressionlevel)as depressionLevel 
from Patients 
left join PatientVisits 
    on Patients.PatientKey=PatientVisits.PatientKey 

，但我得到了以下錯誤：

Msg 8120, Level 16, State 1, Line 1 Column 'Patients.LastName' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

Answer 1

你需要一個GROUP BY添加到您的查詢：

select Patients.LastName, 
    avg (PatientVisits.Pulse)as pulse, 
    avg (patientvisits.depressionlevel)as depressionLevel 
from Patients 
left join PatientVisits 
    on Patients.PatientKey=PatientVisits.PatientKey 
GROUP BY Patients.LastName 

SQL Server要求您的SELECT列表中的任何列不在聚合函數b中e包含在GROUP BY中。由於您在彙總數據時試圖返回Patients.LastName，因此您必須在該組中包含該列。