Databases with SQLite

Second Normal Form

Once you have your tables in 1NF you are ready for the next step:

A 'technical' definition of 2NF:

• It is in 1NF and has a single attribute unique identifier (UID) (in which case every non key attribute is dependent on the entire UID),
or

• It is in 1NF and has a multi-attribute unique identifier, and every regular attribute (not part of the UID) is dependent on all attributes in the multi-attribute UID, not just one attribute (or part) of the UID.

'unique identifier' is mentioned in both conditions. Let's take a closer look.

The goal of 2NF is to eliminate partial dependencies. And of course those are when an attribute that is NOT part of a key, depends on only PART of a composite key (one or more columns used as key), instead of the complete key.

For example, in a database of employees, the employee ID number may partially determine the employee's address, but not the employee's name or other personal information.

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