From the course: Learning Relational Databases

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Third normal form

Third normal form

From the course: Learning Relational Databases

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Third normal form

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- [Instructor] The Third Normal Form follows a similar pattern to the Second Normal Form. But instead of checking against the individual components of a composite primary key, we'll check each non-key column against every other non-key column. Here, we're looking for columns that are functionally dependent on another piece of information that isn't the primary key. This often occurs when two fields are simply stating the same thing in a different way. For instance, you might try storing the state, and the state abbreviation in an address table. Since state abbreviation is entirely dependent on the state, or vice-versa, one of those two fields should be removed from the table. Here's another example using our Explore California tour company. In the table about the various tour packages, we are storing a difficulty rating as both a numeric rating, and a text description of what that number means. You can see that a difficulty of easy should always correspond to a rating of one, and a…

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