Lookup Tables Best Practices: DB Tables… or Enumerations

Generally you should only use enumeration where there is a clear set of items that will not change, e.g. primary colours, or continent names. Otherwise lookup tables with appropriately implemented foreign keys are pretty much always the best option.

There is a possible variation on the lookup table option where you potentially have a large number of lookup tables for simple id/value relationships. A domain/lookup table pair can dramatically reduce this the number of tables required, albeit with some additional coding complexity. In this case you’d have a domain table

DomainID int identity
Domain   varchar(255)

and a key/value table

DomainID int
ID       int identity
Value    varchar(255)

Hence a row is added to the Domain table corresponding to each lookup table that you would otherwise use, and all (key-domain)/value pairs added to the value table. Apart from simplifying the database structure this approach also has the advantage that ‘lookup tables’ can be created in the application code dynamically, which in some applications can be extremely useful.

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