SQL Antipatterns

How to Recognize the Antipattern

If you hear people use phrases like the following, they’re probably practicing the Keyless Entry antipattern:

• “How do I query to check for a value that exists in one table and not the other table?”

  Usually this is to find orphan child rows whose parent has been updated or deleted.

• “Is there a quick way to check that a value exists in one table as part of my insert to a second table?”

  This is to ensure that the parent row exists. A foreign key does this for you automatically and uses any index on the parent table to make the check as efficient as possible.

• “Foreign keys? I was told not to use them because they slow down the database.”

  Performance is often used as a justification for cutting corners, ...