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We need to create a database schema design based on the following (simplified) requirements of the COMPANY Database:
The company is organized into DEPARTMENTs. Each department has a name, number and an employee who manages the department. We keep track of the start date of the department manager. A department may have several locations.
Each department controls a number of PROJECTs. Each project has a unique name, unique number and is located at a single location.
In general, 3 binary relationships can represent different information than a single ternary relationship (see Figure 3.17a and b on next slide)
If needed, the binary and n-ary relationships can all be included in the schema design (see Figure 3.17a and b, where all relationships convey different meanings)
In some cases, a ternary relationship can be represented as a weak entity if the data model allows a weak entity type to have multiple identifying relationships (and hence multiple owner entity types) (see Figure 3.17c)
A number of popular tools that cover conceptual modeling and mapping into relational schema design.
Examples: ERWin, S- Designer (Enterprise Application Suite), ER- Studio, etc.
Serves as documentation of application requirements, easy user interface - mostly graphics editor support
Some of the Currently Available Automated Database Design Tools Data modeling, design/reengineering Visual Basic/C++ Visio Enterprise Visio Data modeling, business logic modeling Enterprise Application Suite Sybase Conceptual modeling up to code maintenance Xcase Resolution Ltd. UML Modeling & application generation in C++/JAVA Rational Rose Rational (IBM) Mapping from O-O to relational model Pwertier Persistence Inc. Data, process, and business component modeling Enterprise Modeling Suite: Erwin, BPWin, Paradigm Plus Platinum (Computer Associates) Data modeling, object modeling, process modeling, structured analysis/design System Architect 2001 Popkin Software Database modeling, application development Developer 2000/Designer 2000 Oracle Database administration, space and security management DB Artisan Database Modeling in ER and IDEF1X ER Studio Embarcadero Technologies FUNCTIONALITY TOOL COMPANY
Extended Entity-Relationship (EER) Model (in next chapter)
The entity relationship model in its original form did not support the specialization and generalization abstractions
Next chapter illustrates how the ER model can be extended with
Consider the ER diagram shown in the previous slide for part of a BANK database. Each bank can have multiple branches, and each branches can have multiple accounts and loans.
List the (strong) entity types in the ER diagram
Is there a weak type? If so, give its name, partial key, and identifying relationship.
What constraints do the partial key and the identifying relationship of the weak entity type specify in this diagram?
List the name of all relationship types, and specify the (min, max) constraint on each participation of an entity type in a relationship type. Justify your choices.
List concisely the user requirements that led to this ER schema design
Suppose that every customer must have at least one account but is restricted to at most two loans at a time, and that a bank branch cannot have more than 1000 loans. How does this show up on the (min, max) constraints?