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key-midterm1-fall2006 - CSCI 485 Midterm I Oct 3 2006(Fall...

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CSCI 485, Midterm I Oct 3, 2006 (Fall 2006) Prof. Shahram Ghandeharizadeh Warm-up (10 Points) 1. (5 points) Write your name and student-id on your blue book. 2. (5 points) What is the difference between the primary key and the candidate key of a table? Provide an example. Candidate key is a minimal superliey that uniquely identifies either an entity or a relationship, e.g., Social security number, phone number. A primary key is a candidate key that is chosen by the database designer to identify the entities of an entity set or relationships in a relationship set. Magnetic Disk Drives (10 points) 3. (5 points) What does a disk do during a seek operation? Reposition its read/write head from their current cylinder to the destination cylinder. 4. (5 points) How does a Record identifier (RID or TID) uniquely identifies the location of a record on the surface of the disk drive? RID is (Page#, Slot#). The DBMS formats the underlying disk drive as a sequence of disk pages numbered from 1 to n. The Page# refers to one of these disk pages.
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