Ch7New2-10 - Chapter 7, Part 2: Conceptual Data Modeling...

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Unformatted text preview: Chapter 7, Part 2: Conceptual Data Modeling Conceptual D. Harrison McKnight Eli Broad College Eli of Business of Essential 2 Know Essential From a written scenario, be able to From correctly draw an ER model, displaying: correctly – Entity types – Relationships – Relationship labels – Attributes (including identifiers) – Subtype-supertypes – Cardinality-Optionality Key terms Advanced Data Modeling Advanced in Systems Analysis Multi-Valued Attributes Multi-Valued What it is: – Repeating attribute or group of Repeating attributes attributes Why it’s a problem: – Redundancy / data integrity – Complexity What to do: – Consider creating a new (weak) entity Multi-Valued Attributes: Multi-Valued What they look like in ER EmployeeName Address Employee_ ID Dep_Name Employee Multi-Valued Attributes: Multi-Valued The Problem—ID, Redundancy The The Fix—Add Weak Entity Employee Entity Employee Empl_ID Empl_name Address Dep. Name 1441576 Jim Henries 4242 Dixon Street Harriet Henries 1087578 Ron James 8987 Main Drag Jan James Jim James Jane James 9898773 Jill Jarnes 7879 Silvan Lane John Harkin Multi-Valued Attributes: Multi-Valued The Fix—Add Weak Entity Address Employee_ ID EmployeeName Dep_Name Dep_Age Dep_ID Dep_Relation Employee Employee Dependent More on Relationships More Degree of a Relationship Degree Number of Participating Entity Types Binary Relationship – Degree 2 Unary Relationship – Degree 1 – Recursive relationship Ternary Relationship – Degree 3 Binary Relationship Binary One-to-One – Both “ends” are 1-1 or 0-1 One-to-Many – One end is 1-1 or 0-1 – Other end is 1-Many or 0-Many Many-to-Many – Ends are 1-Many or 0-Many Unary Relationships Unary marries One-to-One Person is married to One-to-Many manages Employee is managed by is composed of Many-to-Many Part is a component of Ternary Relationships Ternary Part supplies Supplier Project One or more Suppliers supply one or more Parts to one or more Projects Ternary Relationships Ternary Quantity Part supplies Supplier Project Quantity is the quantity of a part provided by a supplier and used on a project. Ternary Relationships Ternary Quantity Part Supply Project The next step… Supplier Associative Entities Associative Relationships that masquerade as Relationships entities entities – Verb-y entities – Event-ish entities Chen’s ER Modeling Technique – Relationships can have attributes – But for ITM311, turn them into entities, and But add cardinality-optionality add Essential 2 Know Essential From a written scenario, be able to From correctly draw an ER model, displaying: correctly – Entity types – Relationships – Relationship labels – Attributes (including identifiers) – Subtype-supertypes – Cardinality-Optionality Key terms ...
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