Consider the Enhanced Entity-Relationship Diagram in Table 2 on the next page an

Question

Consider the Enhanced Entity-Relationship Diagram in Table 2 on the next page and answer the following questions by ONE sentence each. Note that attribute total refers to the total billing amount of an order.

(a) Explain whether there can be an order that is neither a phone order nor a table order.

(b) Which attribute, or set of attributes, uniquely identifies a table?

(c) Explain whether it is possible to compute the total billing amount of all (phone and table) orders placed in one specific restaurant.

Receives_by_phone Restaurant hone_line phone num Contains dateTi me billingNo total Order Originates from Table optional.orh number PhoneOrder TableOrder street wai ter deliveryAddress postcode city

Explanation / Answer

(a) Explain whether there can be an order that is neither a phone order nor a table order.

Ans:--> According to this ER - diagram, Resturant can take only two types of order (1) Table order (2) through Phone Line

So Answer is No.

(b) Which attribute, or set of attributes, uniquely identifies a table?

Ans:--> Table can be identified Table Number.

(c) Explain whether it is possible to compute the total billing amount of all (phone and table) orders placed in one specific restaurant.

Ans:--> Yes there is an entity ORDER (optional), Which contains the record of all orders (Phone + table) and each order can be identified uniquely by Billing Number and total no. of orders can get through Total attribute and so the amount can be calculated.

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