1. You can load the two tables from SQL database, but you need to find out how to link the tables properly. Based on your explanation, the first table is defined by Year and Customer, and the second table only has Customer. Don't you have Year in the second table? Correct linking of the tables is th key to correct reporting/analysis in QlikView. Perhaps you could look up some available training on QlikView scripting. Those issues are covered there.
2. The "sub-sheet" is implemented in an object called "Container". You can list several objects (charts and tables) in a Container, and their names will be presented in tabs.
The recommended is create 2 qvw but if you need to put all in 1 qvw simply load 2 tables:
For the second issue, like luistarzia says, use the "container" object, it allow you put in the same object 2 or more tables, graphics.
1- The object container only support one object by tab.
2- You can link the qvw with SQL if you want or download the data from SQL to Excel and load data in QlikView from Excel.
In the script you can load all you data after the declaration of variables:
SET MoneyFormat='$ #.##0,00;$-#.##0,00';
SET TimeFormat='hh:mm:ss TT';
SET TimestampFormat='DD/MM/YYYY hh:mm:ss[.fff] TT';
HERE LOAD YOUR DATA