要求如下：
The average performance rating (with descriptor associated to the rounded value) by department and sorted lowest to highest.
然后有两个Table，一个Table里包括Performance rating，department的信息，另一个表格是Performance rate以及对应的descriptor。想问一下SQL语句怎么写才对？
我自己写的是
Select Performance_rating, department, descriptor
From Table1
INNER Join Table2
On Table1.Performance_rating = Table2.Performance_rate
Order By Department
但是运行了报错说需要Department有aggregate_function
想问一下怎么解决，谢谢。
根据你的需求，需要用到聚合函数来计算每个部门的平均性能评级。修改你的SQL语句如下：
SELECT Table1.department, ROUND(AVG(Table1.Performance_rating), 0) AS avg_performance_rating, Table2.descriptor
FROM Table1
INNER JOIN Table2 ON Table1.Performance_rating = Table2.Performance_rate
GROUP BY Table1.department, Table2.descriptor
ORDER BY avg_performance_rating;
这个SQL语句将根据部门和描述符计算平均性能评级，并按照升序排序，其中ROUND函数用于将平均值四舍五入到最接近的整数。