Sql query using joins to find sum of quantity

Question

Here,in billtran table the productid=1 is repeated twice

I want to find the sum(billtran.quantity) of each productid separately

select Query1:

 select name,billtran.quantity from product inner join billtran on product.id=billtran.productid where product.id in(select id from product)

Answer 1

Per comment:

select name, SUM(billtran.quantity) from product inner join billtran on product.id=billtran.productid where product.id in(select id from product)
GROUP BY NAME

My additions in caps

Note: where product.id in(select id from product) is an entirely useless where clause and should be removed. Queries don't have to have a where clause and don't need one that says a table id should be in all the ids in that table (always true)

I would hence have written this one as:

SELECT
  p.name,
  SUM(b.quantity) as sumof_quantity
FROM 
  product p
  INNER JOIN billtran b ON p.id=b.productid 
GROUP BY 
  p.name