從sql表中計算每日平均銷售額

Question

我想從我的sql表中計算銷售額的每日平均值。 我嘗試使用下面的查詢，但它給錯誤說「關鍵字附近有語法錯誤選擇」

select avg(select sum(total) from canteen group by date) as average from canteen 

Answer 1

不嵌套聚合函數。這是你想獲得每個日期的總和是什麼：

select avg(total) 
from (select day, sum(total) as total 
     from canteen 
     group by day 
    ) c; 

或者，更簡單的選擇：

select sum(total)/count(distinct day) 
from canteen; 

Answer 2

的

select day, sum(total) 
from canteen 
group by day; 

您可以使用子查詢得到的平均正確的語法是

SELECT date, avg(total) average FROM (
SELECT date, sum(total)total FROM canteen GROUP BY DATE 
)AS A 
grouP BY date 

Answer 3

我pre如果你不打擾嵌套查詢，

select avg(total) from(select sum(total) as total from canteen group by date) as T 

Answer 4

這是更好，如果你嘗試使用這樣的子查詢：

select avg(total) from(select sum(total) from canteen group by date)