4.6 Alternative modeling conventions
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4 Terms
crow's foot notation
Variations in cardinality conventions are common. One popular convention, called crow's foot notation, depicts cardinality as a circle (zero), a short line (one), or three short lines (many). The three short lines look like a bird's foot, hence the name "crow's foot notation".
Intangible Entity
documented in the data model, but not tracked with data in the database.
Selecting Primary Keys
stable: value should not change.
simple: easy to type and store.
meaningless: no descriptive information.
artificial key
An artificial key is a single-column primary key created by the database designer when no suitable single-column or composite primary key exists.
Usually artificial key values are integers, generated automatically by the database as new rows are inserted to the table. Artificial keys are stable, simple, and meaningless.