在SQL查询中使用聚合函数 [英] Using aggregate functions in SQL query

问题描述

我的表格结构如下:

ATT_Table : Fields - Act_ID, Assigned_To_ID, Percent_Complete(Integer value)
Act_ID is primary key, Assigned_To_ID is referenced to Emp_ID in Employee_Table.

Employee_Table : Fields - Emp_ID, F_Name. 
Emp_ID is primary key.

现在在特定时间点，可以将1个或多个活动分配给同一个人.我的目标是编写查询以计算人员的负担.我想计算分配给特定人的活动数量(可以大于1)，然后取其percent_Complete的平均值.

Now at a particular point in time, 1 or more activities can be assigned to same person. My goal is write a query to calculate a person's load. I want to count the number of activities assigned to a particular person (can be more than 1) then take the average of their percent_Complete.

例如，如果给人员A分配了A1，A2，A3(Act_ID).然后对应(Percent_Complete值加法)/3.基本上是平均水平.在我的最终查询结果中，我想要:

For example if person A is assigned A1, A2, A3(Act_ID). Then corresponding (Percent_Complete values addition)/3. Basically an average. In my final query result I want:

Name, Number of activities assigned(Count), load value(Avg). 

我该怎么办?我是否必须使用嵌套的WHERE IN子句?谢谢.

How do I this? Do I have to use a nested WHERE IN clause ? Thanks.

推荐答案

尝试以下操作:

select Emp_ID, F_Name, count(Act_ID), avg(Percent_Complete)
from ATT_Table, Employee_Table where ATT_Table.Assigned_To_ID = Employee_Table.Emp_ID
group by Emp_ID, F_Name

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