Multiple Tables To Create A More Complete List

My SQL knowledge is limited to only trial-and-error and on-the-fly learning, sadly. However, I've had past experience with VB and some earlier, more basic programming, so I don't find it that difficult to grasp; it's just rather overwhelming without any formalized training.

I'm trying now to solve a problem that involves a sales history report. Our sales history table lists only records for product lines which a customer has purchased in the past. However, the budgeting team needs a list of each customer with all product lines, even if they've never purchased, and they'd like to include an industry code value that is from another table.

So the way the tables are looking is this:

Sales_History as the main table with the appropriate data in it
Product_Lines as a reference to fill out the main table with non-purchased lines

Accounts as another reference that gives the industry code per the customer ID in the main table''I'm seemingly on the right track with the following, which tries to create a list of all product lines and the records from sales_history which match them:

SELECT sales_history.sah_sort_id,sales_history.sah_sortkey3,sales_history.sah_sortkey2_desc,
prod_lines.pl_prodline_id,prod_lines.pl_short_desc
FROM dbo.sales_history
INNER JOIN prod_lines ON sales_history.sah_sortkey3=prod_lines.pl_prodline_id

[code]...

However, this produces a list of only 21 rows, when there should be 41.