One to one mapping and one to many mapping in a single table

Question

Hi All,
I am asked to design a banking application, I have CUSTOMER table where the information regarding the customer is stored. I have have an ACCOUNT table where account information is stored.
Now A customer can start all the 3 types of accounts. (Checking account, Saving account and FD(Fixed Deposits))
One customer can have - >Only one checking account only one Saving account, but can have many FD account. How do we implement this using integrity constraints?
CUSTOMER Table -> Cust_id(PK), Cust_name, Cust_phone, Cust_address
ACCOUNT Table -> AccountNo, Acc_type,Cust_id
Your answer is greatly appreciated.
Thanks
Sophy

Answer 1

You may need to create a UNIQUE function based index. That would work for you.
create table customer_1 (Cust_id integer primary key, Cust_name varchar2(100), Cust_phone number, Cust_address varchar2(100))
create table account_1 (AccountNo integer primary key, Acc_type varchar2(100),Cust_id integer references customer_1(cust_id))
create unique index account_idx on account_1 (cust_id, decode(acc_type,'CA',acc_type, 'SA', acc_type, 'FD', 'FD' || accountno))
insert into customer_1 (cust_id, cust_name, cust_phone, cust_address) values (1, 'karthick', 0, 'x')
insert into account_1 (accountno, acc_type, cust_id) values(1, 'CA', 1)
insert into account_1 (accountno, acc_type, cust_id) values(2, 'SA', 1)
insert into account_1 (accountno, acc_type, cust_id) values(3, 'FD', 1)
insert into account_1 (accountno, acc_type, cust_id) values(4, 'FD', 1)
insert into account_1 (accountno, acc_type, cust_id) values(5, 'FD', 1)
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