Dimitri Fontaine, a PostgreSQL major contributor, has written an awesome blog series on PostgreSQL data types to show how to benefit from the PostgreSQL concept of a data type.

The PostgreSQL concept of a data type is more than input validation, a PostgreSQL data type also implements expected behaviors and processing functions. This allows an application developer to rely on PostgreSQL for more complex queries, having the processing happen where the data is — for instance when implementing advanced JOIN operations, then retrieving only the data set that is interesting for the application.

The posts in this series were extracted from his book Mastering PostgreSQL in Application Development — which teaches SQL to developers so they can replace thousands of lines of code with very simple queries.