Symbols in the Data Model

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The dotted box in the top left corner shows the set of objects that are PERSONS.


Primary Key column

2, 3 ...

Alternate (secondary) key column


Foreign Key column


Virtual column: field value is derived from a different base table (also referred to as 'joined column').


Exclusivity rule: each supertype can be ONLY ONE of its subtypes.


Deduction: value (for RESERVATION.GROUP_DISCOUNT) is deduced from (number of related records in the PARTICIPANT table and data in the DISCOUNT table).