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Relational Database Definitions

The following terms deal specifically with Subforms, Posts and Abacii containing Lookup or Sub tiles and refers to how data from two different Relations are linked

  • Link Field
  • Primary Key field
  • Foreign Key Field
  • Source
  • Target

Link Field
Take the example of a Collection containing a "Customer" Relation and a "Phone Calls" Relation. There are several phone call records entered for each customer record. Both Relations contain an "ID Number" Field. Because this Field is common between the two Relations, it is called a Link Field. Another term for Link Field is Key Field.

Primary and Foreign Keys
If you are trying to link records between Relations you would use Primary and Foreign Keys. Because each record in the "Customer" Relation has a unique ID Number, the "ID Number" Field in the "Customer" Relation is a Primary Key Field. On the other hand, each record in the "Phone Calls" Relation may not have a unique ID Number. You may have called the person with ID Number 1 several times. Therefore, the ID Number in the "Phone Calls" Relation is a Foreign Key.

Source and Target
The difference between Source and Target records is best illustrated by considering the Lookup tile. The Lookup tile contains four (4) holes.

The first hole contains the Target Field or Abacus you are looking up. The fourth hole is the Target Relation that you will be looking in. The Links or Keys are in the second and third holes. The second hole of a Lookup tile contains the Target Link. The third hole contains the Source link. The Source Link will trigger the Lookup into action. When the Source Link is defined 9for example, data is entered in the Source Link Field on a View), the Lookup will search the Target Relation for a record where the Source Link field equals the Target Link Field. When it finds the record, data from the Target Field in the first hole becomes the result of the Abacus.