Calculating the Difference Between Two Values in the Same Column using group by in mysql

Question

I have a table as shown below. I want to do a partition and then subtract the values in the same column and different rows to get the difference using group by.

id	type	name	amount
1	sale	sam	2
2	sale	sam	15
3	return	lilly	20
4	sale	lilly	25
5	return	sam	3
6	sale	anju	20

And Need to return:

name	amount
sam	14
lilly	5
anju	20

Answer 1

Your sample data is a little suspect but I think you basically need to apply a case expression to your sale type :

select name,
    Sum(amount * case when type='return' then -1 else 1 end) Amount
from t
group by name;