Database Question 4. For the Personnel entity shown in Figure 2, give an example

Question

Database Question

4. For the Personnel entity shown in Figure 2, give an example non-empty instance using made-up but realistic-looking data (not just random characters and numbers). Use the bracket [ ] and brace { } notation from the class notes for your example, if appropriate.

5. Consider the schema in Figure 2 as an enterprise schema. Explain what is meant by logical data independence using a subset of the schema (selected entity or entities, attribute(s), and relationship(s)) as a view or external schema.

3n 1 nerme Owner keeps Figure 2. Charter Boat Entity Relationship Diagram (ERD) Iti Iventory ecquips Boat shi p ID# 1 imID hires nunber hame Iti 1 has crew Personnel Renter atranges Charter 33n neme position date title rank

Explanation / Answer

1.

Personnel Entity:

Name Number Title Rank

Sameer 9876356278 Manager 3

John 9453618836 Captain 1

Ketty 8926739273 Vice Captain 2

Bill 8929988877 Worker 4

Jenny 6792727838 Worker 4

Amanda 9232123232 Head Worker 3

Jimmy 9738378282 Care Taker 4

2.

Logical Independence of Data means if you make any changes to schema will not affect the current data in database. e.g. Consider Owner entity adding one more attribute as DOB or perosnol information to it will not affect the schema already present. And you can easily set the values of DOB for already filled entries without any furhter modification to given schema.

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