Database Systems 6th Edition by Ramez Elmasri, Shamkant B. Navathe

تمرين 17

This exercise asks you to converting business statements into dependencies. Consider the following relation DiskDrive(serialNumber, manufacturer, model, batch, capacity, retailer). Each tuple in the relation DiskDrive contains information about a disk drive with a unique serialNumber, made by a manufacturer, with a particular model, released in a certain batch, which has a certain storage capacity, and is sold by a certain retailer. For example, the tuple DiskDrive(1978619, WesternDigital, A2235X, 765234, 500, CompUSA) specifies that WesternDigital made a disk drive with serial number 1978619, model number A2235X in batch 765235 with 500GB that is sold by CompUSA.
Write each of the following dependencies as an FD:
a. The manufacturer and serial number uniquely identifies the drive
b. A model number is registered by a manufacturer and hence can't be used by another manufacturer.
c. All disk drives in a particular batch are the same model.
d. All disk drives of a particular model of a particular manufacturer have exactly the same capacity.