Why on earth are you guys trying to backward translate to make a link to the original post, this will lead to 404!
All you have to do is make a relation to the post's ID. For instance; "website.com/hello-world" is using %post% permalink but the real id is 25. So you make a relation of the translated post value to the id of the original posts
In one db table called "translations" you could have all the different translation for page/post with ID 5 and it will be a "One to many" relationship as one post could have many translations but all those translations can only belong to one post.
trans_id trans_value trans_code post_id 1 hola-mundo es 5 2 ciao-mondo it 5 3 hallo-welt de 5
How ever, can you imagine how big your db will get?