PostgreSQL, Second Edition

Internal and External Forms

Before going much further, it is important to understand the difference between the external form of a value and the internal form.

The external form of a data type defines how the user enters a value and how a value is displayed to the user. For example, if you enter a numeric value, you might enter the characters 7218942. If you enter these characters from a client that uses an ASCII encoding, you have entered the character values 37, 32, 31, 38, 39, 34, and 32 (in hexadecimal notation). The external form of a data type is used to interact with the user.

The internal form of a data type defines how a value is represented inside the database. The preceding numeric value form might be translated from the string 7218942 ...