The query is executing very slowly, is there any way to improve it any further?

Question

I have the following query, and because of a lot of SUM function calls, my query is running too slow. I have a lot of records in my database and I would like to get

Answer 1

To improve the speed of SQL query, you must add indexes. For each joined table, you have to add one index.

Like this code example for oracle:

CREATE INDEX supplier_idx
ON supplier (supplier_name);