Query to find customers that have deposit in all branches located in a specific city
I have two solutions for your question :
solution 1 , I use Not Exists , Except

Select distinct C.CustomerName
From customers C
where NOT EXISTS ((Select BranchName
                   From Branch
                   Where BranchCity='Bahar')

                      EXCEPT

                   (Select BranchName
                    From Deposit a
                    where A.CustomerName = C.CustomerName))


In solution 2 I use Not Exists ,

Select Distinct C.CustomerName
From Customers C
Where NOT EXISTS  (Select BranchName
                   From Branch b
                   Where BranchCity='Bahar'
                   and NOT EXISTS (select BranchName
                                   from Deposit a
                                   where a.CustomerName=C.CustomerName
                                   and a.BranchName=b.branchName))


Each one of the query above will answer your query and give you the desired result.