如何将两个字段相乘然后得到平均行数

Question

I want to make avg of grades

there is a table like this (INNER JOIN of two table)

+-------+------+
| grade | unit |
+-------+------+

I want to get multiply of (grade & unit) as res

then, get avg of res

I can do it by php, but i need to make it only with one sql and the result must be in

one field

thank alot

Answer 1

SELECT AVG(grade * unit) FROM ...

Answer 2

select grade,unit, AVG(grade *unit) as average from ...