I Need to display 2 table using oracle databse and BDC. one table need to be associate to another table.

I have done this. But 2 following issues i am facing:-

1. If data is null of 1st table and i click on that rows then it throws error in next table as well as in first table more then 1 radio button select.

2. Reader (Domain Users) are not able to see these table and throws error that unable to connect database, where as i have given ID and Pwd in BDC config file.

Any pointer will be appreciating lots.