zeshanazam,
Ideally, you would just limit the output in the code. But if you have to only have it output on one row, try the following. I'm assuming you're using SQL Server. Different database may change the syntax.
Select CASE i.Installment_no
WHEN 1 THEN c.Loan_id
ELSE null
END AS Loan_ID
,i.Installment_no
,i.Date
,i.Amount
from Customer c
,Installments i
,Loan l
where l.Loan_id = c.Loan_id
and c.Loan_id = i.Loan_id;
Hogan