Accounts acctNo owner userid password balance 365556 Tony Jones tjones 456 819.3
ID: 3714255 • Letter: A
Question
Accounts
acctNo
owner
userid
password
balance
365556
Tony Jones
tjones
456
819.37
499872
Frank Smith
fsmith
123
590.81
761112
George Powers
gpowers
geo
239.41
765552
Betty Davis
bdavis
atl
356.21
872221
Suzanne Austin
suze
suze
622.22
899900
Mary Wilson
mwilson
mary
772.12
Customers
cid
cName
cAddr
cPhone
cEmail
tjones
Tony Jones
Miami, Fl
514-999-2131
tjones@yahoo.com
fsmith
Frank Smith
Dallas, Tx
616-423-1717
fsmith@haotmail.com
gpowers
George Powers
Chicago, Il
612-901-2312
gpowers@bellsouth.net
bdavis
Betty Davis
Nashville, Tn
909-367-9485
bdavis@yahoo.com
suze
Suzzane Austin
San Diego, Ca
201-565-1902
suze@yahoo.com
mwilson
Mary Wilson
Atlanta, Ga
405-787-2911
mwilson@hotmail.com
Did you notice a mistake in the database above. “Suzanne Powers” name is different in the second table. What changes could you make to prevent an error like this from occurring again?
Accounts
acctNo
owner
userid
password
balance
365556
Tony Jones
tjones
456
819.37
499872
Frank Smith
fsmith
123
590.81
761112
George Powers
gpowers
geo
239.41
765552
Betty Davis
bdavis
atl
356.21
872221
Suzanne Austin
suze
suze
622.22
899900
Mary Wilson
mwilson
mary
772.12
Explanation / Answer
The given problem can be prevented by declaring the referential integrity between the two table Accounts and Customers. In table Account 'userid' needs to be declared as Primary key and cid (foreign key) field of Customer table will refer to the userid of the Account table.
WHen the referential integrity constraint is established there will be no need to of field cName in Customer table.
The new relational schema is given beow. Underlined attributes are primary key and bold are foreign key.
Account (acctNo, owner, userid, password, balance)
Customer (cid, cAddr, cPhone, cEmail)
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.