Help with client database?

I need help updating a client database at work. The main purpose if it is to keep track of sales per client, but at the moment, there are a lot of columns with client info and I need to add even more.

My idea is to split this into 2 lists, one with sales and one with all the info. But is there a way I can link these lists? In other words, if I'm looking at the sales list and decide that I need some info about that client (for instance look up his e-mail address or phone number) directly, without having to open the second list and having to search through it again? Maybe even summarize some info about that client in the second list?

Thanks.