SQL：为另一列的唯一条目平均一列的值

Question

Suppose I have a table with columns:

a CHAR, b Int, c Int

Column a only has entries of x/y/z, and the values in b and c go from 1 to 10.

Then I do:

select a, c 
from mytable 
where b > 5

What would I have to do from here to get a table of 3 rows (one for each letter), and the average c value for each of x, y and z?

Answer 1

Are you looking for group by ?

select a, avg(c)
from t
where b > 5
group by a;