Test 2 Notes

Test 2 Notes - Line of demarcation (between conceptual and...

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Line of demarcation (between conceptual and internal) – choose DBMS software (IBM or Oracle…) Attributes 1. Required v. Optional 2. Domain – stuff about the values (character or numeric, length, specific values) 3. Identifiers/Keys – all super keys - CUID #, network ID, SSN composite – multiple attributes 4. Composite v. Simple – composite – can it be subdivided (zip code can be split into first five and last four, then can make first 5 required and the last four not) simple – no subdivision is possible 5. Single v. Multi value – e.g. phone, email, address could create different columns but better to make separate entities 6. Derived attributes – GPA, age Relationships 1. Connectivity – classification of 1:1 (tolerate), 1:M (ideal) and M:N (cannot) 2. Cardinalities – crow’s feet is many side and line is for one side (0,4) – professor can teach between 0 and 4 classes – optional, don’t have to offer classes, there can be no rows on many side (1,4) – must teach at least one class Relationship Strength Existence dependence (strong, identifying)= foreign key is part of PK, can’t set up class
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Test 2 Notes - Line of demarcation (between conceptual and...

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