PostgreSQL provides two methods for implementing user-defined data types through the following commands:
CREATE DOMAINcommand allows developers to create a user-defined data type with constraints. This helps in making the source code more modular.
CREATE TYPEcommand is often used to create a composite type, which is useful in procedural languages, and is used as the return data type. Also, one can use the create type to create the
ENUMtype, which is useful in decreasing the number of joins, specifically for lookup tables.
Often, developers tend not to use the user-defined data types, and use flat tables instead due to a lack of support on the driver side, such as JDBC and ODBC. ...