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Self join Relationship or New Table?

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In my solution, I have a "Personell" table which includes about 400 records.

Personell is distinguished, according to its specialty to :

  • mechanic
  • electrician
  • driver

Some fields in this table hold attributes that are common to all records(Personell) like:

  • DOB
  • Address
  • Phone number
  • Email et.c.

On the other hand, each specialty has its own unique attributes. For example "drivers" have:

  • licence ID
  • licence type
  • Total hours behind wheel et.c.


Should I put the fields that hold specialty-unique attributes, to my main table ?


Put them on  a related table that holds only the _pk of each Person , and make a script to populate

the new table each time I have a new entry on the old?



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Both solutions are valid and which one you choose depends on details that we don't have - and to a large extent on your personal preference.

Implementing the second solution (a.k.a the supertype/subtype model) in Filemaker is not trivial, and if the number of the specialty-specific fields is not very large, you may well prefer to keep them all in the same table.

There's also a third alternative in the form of an entity-value-attribute table: https://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model


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