Application domain. Consider a simple banking application in which customers per

Question

Application domain. Consider a simple banking application in which customers perform transactions on some of their accounts. For this purpose we have the database schema that consists of the following three relation schemata: CUSTOMER Cid, name, phone ACCOUNT num, type, desc TRANSACTION num, type, cid, time, amount Domains of attributes have been omitted. The following relations constitute a database, which we denote by db. ACCOUNT CUSTOMER phone num type desc cid name cl Jack 02102205945 01 cheque expenses c2 Jill 02102205945 02 cheque expenses c3 Jill 02259682104 02 online expenses TRANSACTION num type cid time amount 01 cheque cl 24-03-14 09:32 100 01 cheque cl 24-03-14- 22:11 100 02 cheque c2 24-03-14- 22:11 100 02 online c3 24-03-14- 22:11 +100

Explanation / Answer

Option D is true,

It will returns cid which id always used an online and saving account.

Because first part of is return the cid of customers who have not type online means this part is returns the cid of saving type and second part is return the cid of customers who have not type saving means this part is return the cid of online type ids,

And now both parts union is return the Cids of customers who have type online and saving.

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