BU486 Chapter Notes - Chapter 18: Unique Key, Financial Statement
Chapter 18 – Implementing a REA Model in a Relational Database
Combining REA Diagrams
• Individual REA diagrams can be combined to form an integrated REA diagram by:
o 1.) Merging redundant resource entities, e.g. inventory is acquired in expenditure cycle
and reduced in the sales cycle
o 2.) merging redundant event entities, e.g. disburse cash event appears in the
expenditure cycle and the payroll cycle
Integrated REA Diagram Rules
• Every event must be linked to at least one resource
• Every event must be linked to two agents who participate in that event
• Every event that involves the disposition of a resource must be linked to an event that involves
the acquisition of a resource (give-get exchange)
• Every resource must be linked to at least one event that increments that resource and to at least
one event that decrements that resource
• If event A can be linked to more than one other event, but cannot be linked simultaneously to
all of those other events, then the REA diagram should show that event A is linked to a minimum
of 0 of each of the other events
• If an event can be linked to any one of a set of agents, then the ERA diagram should show that
event is linked to a minimum of 0 of each of those agents
Using an Rea Diagram to build a relational database
• Create tables for each distinct entity and M:N relationship
• Assign attributes to each table
o Identify primary keys
o Concatenated keys for M:N relationship table
• Use foreign keys to implement 1:1 and 1:N relationships
Using REA Diagrams to Retrieve Information
• Journals – information contained in event tables
• Ledgers – information contained in resource tables (increment and decrements of events)
• Financial statements – information contained in resources and events using a set of queries
• Management reports – financial and nonfinancial information
Key Terms
• Concatenated Keys – two or more primary keys of other database tables that, together become
the unique identifier or primary key of an M:N relationship table
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