SQL: customers with account in Dharan

The customer's name is in Depositor, the branch is in Account, and the two are linked by acc_no. So we join Depositor and Account and filter on the branch name. DISTINCT removes repeats when a customer has more than one account in the branch.

Using a join

SELECT DISTINCT d.customer_name
FROM   Depositor d
JOIN   Account   a ON d.acc_no = a.acc_no
WHERE  a.branch_name = 'Dharan';

Using a subquery

SELECT DISTINCT customer_name
FROM   Depositor
WHERE  acc_no IN (SELECT acc_no
                  FROM   Account
                  WHERE  branch_name = 'Dharan');

Relational algebra

Π customer_name (σ branch_name = 'Dharan' (Depositor ⋈ Account))

Sample (tested): Sujan holds accounts 1 and 2, both in Dharan, so the output is just Sujan once.