Designing a database structure for a relational database follows the same pattern, regardless of the application development environment. The systems analyst works out a way of representing a real world problem as a set of entities.
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Customer |
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Material |
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Order |
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Order Line |
Each entity can have a one-to-one, one-to-many or many-to-one relationship with another entity. Entity pairs with many-to-many relationships are not allowed; they must be eliminated by the introduction of a new intermediary entity offering many-to-one relationship with one of the original entities and a one-to-many relationship with the other. In this way each entity may remain in third normal form. These entities can then be represented as tables on the database.
A database design can be produced using a range of methodologies including Jackson and SSADM. You can produce a design by hand or using a Computer Aided Software Engineering (CASE) tool. The design should include the following characteristics:
A description of the data elements in a system.
An indication of the relationships between the data elements
Typical modelling techniques for producing a DP4 database design are as follows: