SQL Antipatterns

How to Recognize the Antipattern

If you hear statements like the following, it’s a clue that the Polymorphic Associations antipattern is being employed:

• “This tagging schema allows you to associate a tag (or other attribute) with any other resource in the database.”

  As in EAV, you should be suspicious of any claims of unlimited flexibility.

• “You can’t declare foreign keys in our database design.”

  This is another red flag. Foreign keys are a fundamental feature of relational databases, and a design that can’t work with proper referential integrity has a lot of problems.

• “What’s the entity_type column for? Oh, that tells you which thing this other column points to.”

  Any foreign key must reference the same table on all rows.

The Ruby ...