Busi 335 copyright 2009 10 ym cheung william tan and

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Unformatted text preview: Carson Woo Brown F (778) 820-9829 $35,000 • How about providing an index for each of Emp#, FirstName, LastName, and Phone? FirstName LastName and Phone? 23 BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 24 Direct (Random) Access Method – An Example Example Direct (Random) Access Method Direct (Random) Access Method • uses a mathematical formula called a Advantages: • Rapid access to records; • Sorting is not required. Disadvantages: • Conflict of addresses addresses randomizing algorithm or a hashing algorithm to translate the key field directly into the record's physical storage location on disk. di Address: 501 122454 BUSI 335 Data records Mathematical Operations Address: 515 125555 Add remainder to displacement address (10) (10) Address: 620 134555 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 25 BUSI 335 Direct (Random) Access Method – An Example (cont’d) Example (cont Remainder Displacement after factor + = Record division (initial address storage Record Key by seven of file area) address 1 15 1 10 11 2 17 3 10 13 3 11 4 10 14 4 22 1 10 11 Randomizing computation (÷ 7) File storage area Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 26 Comparing Access Methods Access Methods • Access Speed • Storage Space Overflow Overflow Conflict of addresses Conflict of addresses BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 27 BUSI 335 Co...
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This document was uploaded on 03/04/2014 for the course COMM 335 at The University of British Columbia.

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