1NF Normal Form

  • If a relation contain composite or multi-valued attribute, it violates first normal form
  • A relation is in first normal form if every attribute in that relation is singled valued attribute.
  • Practical Note : It would be trouble some to keep phone number or email id as a different entries and also would be tempting too to put email ids and phone numbers in different table but suppose a requirement comes up where you have to black list email ids in your entire product or you have to black list set of phone numbers then it would be a very huge task to handle it.
  • The important question here you need to ask the requirement is is the phone number or email id’s a valued attribute i.e is there a possibility that any change will occur in future in respect to that attribute like back listing some email ids or phone numbers or blacklisting some domains or county code.
  • And if yes the email id or phone number is a valued attribute then you need to add field (column in DB) is_enabled so that you can disable to enabled these email ids or mobile numbers at anytime.

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