Unable to join 6 tables with out any primary or foreign keys - Out of memory

I have six tables, which unfortunately does not have any primary/foreign key-relations encoded. I've tried to create a view, however I am more than happy with just a table.

I've managed to join the six tables, but after returning 33.5 million rows (cleanInventtrans has 1.7 million rows and every time more tables are added, I am assuming the tables are multiplied by the combination of the previous table) I run out of memory. Now, I realize this is not the correct way of doing this, if it was I'd get a result I am assuming.

I've looked at a couple of questions online
http://www.daniweb.com/web-development/databases/ms-sql/threads/123446/problem-using-join-with-six-tables
SQL joining 6 tables
Unable to relate two MySQL tables (foreign keys)

And I've looked at
http://www.techonthenet.com/sql/joins.php

However, they assume there is a primary-foreign key relationship, my tables do not have this but there are fields which correspond, between the various tables, as seen in the SQL code below. I use these to match up the tables, but somewhere along the line, I am clearly doing it wrong.

I understand that by doing it like this I am essentially multiplying results with each table I join with. I was hoping there was a more clever/correct way of doing it which reduces the amount of results to a management size.

I am unfortunately unable to provide a create statement.

The code I am using:

SELECT     dbo.AX_SALESLINE.SALESID, dbo.AX_SALESLINE.ITEMID, dbo.AX_SALESLINE.QTYORDERED, dbo.AX_SALESLINE.SALESPRICE, dbo.AX_SALESLINE.LINEPERCENT, 
                  dbo.AX_SALESLINE.LINEAMOUNT, dbo.AX_SALESLINE.SALESQTY, dbo.AX_SALESLINE.CONFIRMEDDLV, dbo.CleanInventTrans.COSTAMOUNTPOSTED, 
                  dbo.CleanInventTrans.DATEPHYSICAL, dbo.AX_CUSTPACKINGSLIPJOUR.DELIVERYDATE, dbo.AX_SALESTABLE.CUSTACCOUNT, dbo.AX_SALESTABLE.SALESTYPE, 
                  dbo.AX_SALESTABLE.SALESSTATUS, dbo.AX_CUSTPACKINGSLIPJOUR.QTY, dbo.AX_PRODTABLE.PRODID
FROM         dbo.AX_CUSTPACKINGSLIPJOUR INNER JOIN
                  dbo.AX_SALESTABLE INNER JOIN
                  dbo.CleanInventTrans INNER JOIN
                  dbo.AX_INVENTTABLE ON dbo.CleanInventTrans.ITEMID = dbo.AX_INVENTTABLE.ITEMID INNER JOIN
                  dbo.AX_PRODTABLE ON dbo.AX_INVENTTABLE.ITEMID = dbo.AX_PRODTABLE.ITEMID INNER JOIN
                  dbo.AX_SALESLINE ON dbo.AX_INVENTTABLE.ITEMID = dbo.AX_SALESLINE.ITEMID ON dbo.AX_SALESTABLE.SALESID = dbo.AX_SALESLINE.SALESID ON 
                  dbo.AX_CUSTPACKINGSLIPJOUR.SALESID = dbo.AX_SALESLINE.SALESID

Edit: Salesline and salestable can be related via P/F-keys, however inventtable and salesline does not have a relationship beyond having a column named itemid, which is the same in both. But these have duplicates and can not function as keys.

Edit2:

Salesline and inventtable cannot be related for some reason:

'AX_INVENTTABLE' table saved successfully
'AX_SALESLINE' table
- Unable to create relationship 'FK_AX_SALESLINE_AX_INVENTTABLE'.  
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint   "FK_AX_SALESLINE_AX_INVENTTABLE". The conflict occurred in database "VS1", table  "dbo.AX_INVENTTABLE", column 'ITEMID'.

I've checked the itemid in inventtable, it is unique, and there are multiple of the itemid in the salesline - however not all ID's are numerical in nature, some contain letters. I am not sure if this is what is causing the problem yet.

Edit3:
Foreign-primary relation fails because there are IDs in salines which are not present in the inventtable. Very odd.