Use table with multiple rows with the same value - sql

Question

I'm trying to do a INNER JOIN and count values with information from two tables. The problem is that the product category table have multiple rows with the same or similar value and my COUNT() is to high as a result.
My two tables
Sales table
Date prod_id
2016-01-01 81
2016-01-01 82
2016-01-01 81
2016-10-01 80
2016-01-01 80
2016-01-02 80
2016-01-02 80
2016-01-02 81
2016-01-02 81
.... ....
Product table
prodid Name
80 Banana
81 Apple
82 Orange
83 Ice Cream
80 BANANAS
81 APPLE
82
83 Ice Cream
.... ....
When I do an INNER JOIN and count the number of occurrences of e.g. prod_id I get an unreasonable high number, and my guess is that it's because there are more than one occurrence of prod_id 80 for example.
Do you have any idea for a solution? My first reaction was to redo the Procuct table, but there are many other systems depending on that table so I can't change it a foreseeable future.
My query so far:
SELECT
pt.Date AS "Date",
ft.Name AS "Product",
COUNT(ft.Name) Number
FROM SALES as pt
INNER JOIN PROD_TABLE AS ft ON pt.prod_id=ft.prodid
WHERE pt.Date BETWEEN '2016-01-01' AND '2016-01-30'
GROUP BY pt.Date, ft.Name
ORDER BY pt.Date DESC
Expected result:
Date Product Number
2016-01-01 Banana 2
2016-01-01 Apple 2
2016-01-01 Orange 1

Answer 1

First, you should fix the data. Having a product table with duplicates seems non-sensical. You shouldn't try to get around such issues by writing more complex queries.
That said, this is pretty easy to do in SQL Server. I think outer apply is appropriate:
select p.name, count(*)
from sales s outer apply (
(select top 1 p.*
from product p
where p.name is not null and
p.prodid = s.prod_id -- note: the columns should have the same name
) p;

Answer 2

I guess this simple query solves your requirement:
select
date,
name,
count(name)
from product p inner join sales s
on s.prod_id=p.prodid group by date,name