count rows with same value and get column from other table

I'm trying to count product numbers for a period of time there are three tables.

invoice (table)
Column                   Column           
------------------------------------------- 
|invoicenumber (string) | datefinish(date)|
|A12345                 | 01/29/2015      |
|A12346                 | 01/30/2015      |
|A12347                 | 01/30/2015      |
------------------------------------------ 
invoiceDetails (table)
---------------------------------------------------------------
|invoicenumber (String) |productnumber (long)| Quantity(Short)|
|A12345                 |12345               |  2             |
|A12346                 |1244                |  1             |
|A12347                 |1244                |  3             |
---------------------------------------------------------------

products (table)
------------------------------------
|name(String) |productnumber(long)  |
|Book         | 12345               |
|Newspaper    | 1244                |
-------------------------------------

Here is the result I would like to get:

01/29/2015 2 Book 12345
01/30/2015 4 Newspaper 1244

I need the result set to include the: datefinish, name, productnumber and the count of the productnumber by datefinish order by datefinish, productnumber.

I can get a count of all productnumbers from the invoiceDetails like this.

select i.productnumber , c.cnt from invoicedetails i
       INNER JOIN (SELECT productnumber , count(productnumber ) as cnt
        FROM invoicedetails GROUP BY productnumber ) C ON i.productnumber = C.productnumber 

But if I add another table in the select i get and error and if I add a where in the JOIN i get and error. I tried to just get all but then I get a error: 'Invalid comparison or operation on strings with different collations.'

Select d.productnumber, p.name, t.datefinish from invoicedetails d, invoice t, product p where d.invoicenumber = t.invoicenumber and
d.productnumber=p.productnumber and t.datefinish >= '01/01/2015' and t.datefinish <= '01/31/2015'
order by t.datefinish, d.productnumber

Advantage Database by SAP

Thanks for any help, Kim