Pradip,
Full outer join will give NULL values for Table1(T1): CUSTOMER if we did not get data in Table2(T2): SALES_ORDER for that customer id.In simple way, you are getting NULL values for Customer Id = C4 because table2 does not have rows with customer id C4.
=>If you are talking about all the records from T1 and the matching records from T2 then you are talking about the "LEFT JOIN" and not the "FULL OUTER"
If you want all customer id should be display in final table then use inner join.Because inner join does not contains null values.And parent table should have all customer id.
=>All the customerid's from both the tables will not be retrieved using the "INNER JOIN" "Only the matching records will be retrieved"
I wonder how you can achieve the functionality of a full outer with a left join, and how you must have retrieved all the tuples using the inner join.
B R,
krishna.