exam2.1.docx - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 ISYS 464 Section 1 Spring 2019(Beckman Exam#2 Answer 10 questions

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ISYS 464, Section 1, Spring, 2019 (Beckman): Exam #2 Answer 10 questions total ; 2 on each page plus any other 2. Print your name on the back of the last sheet. What is the purpose of physical database design? Purpose: translate the logical description of data into technical specifications for the storing and retrieving data Goal: create a design for storing data that will provide: » adequate performance AND insure » database integrity » security » recoverability What is a “block factor”? Why is it important in physical database design? Blocking factor: the number of physical record per page Physical Record: a group of fields stored in adjacent memory location and retrieve as a unit How is the next block of data records found in contiguous block allocation ? 1. Contiguous allocation: blocks are used in order » advantage: faster retrieval » disadvantage: harder to insert records 2. Linked allocation: blocks are split up pointer: used to find the next block in the “chain” » advantage: easier to insert records » disadvantage: slower retrieval What is a database index ? In general, describe how it works. Index : a separate table used to determine in a file the location of records that satisfy some condition Indexed file organization : the storage of records either sequentially or non-sequentially (heaped) with an index that allows software to locate individual records Primary keys are automatically indexed Other fields or combinations of fields can also be indexed; these are called secondary keys (or non- unique keys) 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
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How are the SQL statements “ALTER TABLE ADD COLUMN” and “INSERT INTO” different? ALTER TABLE statement allows you to change column specifications: Adds one or more rows of data
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