A functional dependency is said to be transitive if it is indirectly formed by two functional dependencies. For e.g.

X -> Z is a transitive dependency if the following three functional dependencies hold true:

- X->Y
- Y does not ->X
- Y->Z

**Note:** A transitive dependency can only occur in a relation of three of more attributes. This dependency helps us normalizing the database in 3NF (3^{rd} Normal Form).

**Example**: Let’s take an example to understand it better:

Book |
Author |
Author_age |

Game of Thrones | George R. R. Martin | 66 |

Harry Potter | J. K. Rowling | 49 |

Dying of the Light | George R. R. Martin | 66 |

{Book} ->{Author} (if we know the book, we knows the author name)

{Author} does not ->{Book}

{Author} -> {Author_age}

Therefore as per the rule of **transitive dependency**: {Book} -> {Author_age} should hold, that makes sense because if we know the book name we can know the author’s age.

Jennifer says

December 7, 2016 at 2:17 AM{Book} ->{Author} (if we know the book, we knows (KNOW*) the author name)