Data Management and Development Notes

1423456 1223232 instructor name grade james buck b

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Unformatted text preview: either pilot or copilot on any trip 34 CUSTOMER 1 requests M CHARTER M copilots M pilots 1 1 PILOT 1 is an 1 EMPLOYEE M requires 1 AIRCRAFT M has a 1 MODEL Normaliza9on •  A process for assigning acributes to en99es •  Produces good table structures •  Reduces data redundancies to prevent: –  Update anomalies –  Addi9on anomalies –  Dele9on anomalies Normaliza9on •  Generally, normaliza9on would follow en9ty- rela9onship modeling –  Normaliza9on will catch any errors in the E- R process –  Introducing new acributes may require addi9onal en99es and normaliza9on will catch these problems –  With simple databases, normaliza9on can be applied directly to current reports or spreadsheets Poor table structure AC_NUM AC_MODEL AC_RENT_CHRG AC_SEATS AC_TOTAL TIME 1178R Cessna C- 172 Skyhawk 58.5 4 4512.6 2051Y Cessna C- 172 Skyhawk 58.5 4 5325.5 2087V Cessna C- 152 Commuter 51.75 2 4889.8 2268R Cessna C- 172 Skyhawk 58.5 4 4299.6 2867W Piper PA28- 181 Archer II 64 4 3267.4 3213R Piper PA28- 181 Archer II 64 4 2517.9 4112E Piper PA28- 181 Archer II 64 4 5211.3 45ZU Cessna C- 152 Commuter 51.75 2 7003.2 5725Y Cessna C- 172 Skyhawk 58.5 4 3968.2 Good table structure Table: Aircrau AC_NUM AC_TOTAL TIME MOD_ID 1178R 4512.6 C- 172 2051Y 5325.5 C- 172 2087V 4889.8 C- 152 2268R 4299.6 C- 172 2867W 3267.4 PA28- 181 3213R 2517.9 PA28- 181 4112E 5211.3 PA28- 181 45ZU 7003.2 C- 152 5725Y 3968.2 C- 172 Table: Model MOD_ID C- 172 C- 152 PA28- 181 MOD_RENT_ MOD_MANUF MOD_DESCR CHRG MOD_SEATS Cessna Skyhawk 58.5 4 Cessna Commander 51.75 2 Piper Archer II 64 4 Dependence •  Acribute B is dependent on acribute A if whenever the value of A is x, the value of B is y •  Acribute A determines acribute B if all of the rows in the table which agree for A must also agree for B •  Example: –  Student Number - > Student Name –  Employee SIN - > Employee Name Dependence •...
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This document was uploaded on 02/14/2014.

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