Question

I have data in the following format :

TYPE AMOUNT
Book   £2
Pen    £1
Book   £3

I’m trying to output this as a weighted average :

TYPE Weighted Average
Book 0.833333333
Pen  0.166666667

So far I have :

Select TYPE, AMOUNT/SUM(AMOUNT) 
FROM MyTable
Group by TYPE

Answer 1

This should give you the result you want:

select type
    , cast(sum(amount) as decimal(10,5))/(select sum(amount) from t)
from t
group by type

See Sql Fiddle for Demo