SQL：如何在一条SQL语句中查找总数和平均值？

Question

我想计算支出的总量和计算从行数的平均值是这样的：

SELECT AVG(SUM(expenditure)) from INCOME; 

然而，有一个错误说“聚集函数和的滥用（）”

我该如何做到这一点？

Answer 1

由于总数只有一个，所以无法计算总和的平均值。

平均值AVG()函数已经计算出总数作为其逻辑的一部分。

这是你想要什么：

SELECT AVG(expenditure) as AverageExpenditure, 
     SUM(expenditure) as TotalExpenditure 
from INCOME; 

Answer 2

SELECT AVG(expenditure) AS avg_exp, SUM(expenditure) AS sum_exp FROM INCOME;