Relational Databases using Filemaker Pro 4.0 Contents
David Remsen
Relational Databases

Relational databases data collections that are represented by more than table. This a common and powerful means to store data and it is employed for some of the following reasons.

  • Eliminates redundant data representation.
  • Organizes data logically
  • Represents logical hierarchies

A RDBMS (R="relational") has specific mechanisms for declaring and maintaining the relationship between related tables BUT the logical relationship is implicit in the data schema (the table columns) itself.

 The Key to a relational database - Two tables can be said to be related if they contain a common column element that allows one or more rows to be logically linked together. It doesn't matter if the tables are in the same file or even within the same "database." The column that links them is the "key" field. In this case we create an artifical key field called ID. The number is unique for each person. We might also choose to use some other unique value such as Social Security Number.
ID Last First Age
001 Roberts David 37
002 Smith Catherine 25
ID Test Results
001 Pulse 75
001 Blood Pressure 105/76
001 Respiration 45
002 Pulse 81
Each person as a unique ID. We can relate tests to people by referring to the ID column in each table. A quick scan of the two tables reveals that David Roberts had three tests and Catherine Smith had one.
Next: Types of Relationships
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