聚合函数或GROUP BY子句

本文介绍了聚合函数或GROUP BY子句的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我使用了以下查询:

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

但是出现以下错误:

推荐答案

您需要在查询中添加GROUP BY:

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SELECT列表中未包含在聚合函数中的所有列都包含在GROUP BY中.由于要在汇总数据时尝试返回Patients.LastName，因此必须将该列包括在分组依据中.

SQL Server requires any columns in your SELECT list that are not in an aggregate function be included in a GROUP BY. Since you are trying to return the Patients.LastName while you are aggregating the data you must include that column in a group by.

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