Introduction to SQL: Mastering the Relational Database Language, Fourth Edition/20th Anniversary Edition

Chapter 33. User-Defined Data Types, Functions, and Operators

Introduction

Chapter 5, “SELECT Statement: Common Elements,” described data types as INTEGER, CHAR, and DATE. These are the so-called base data types and are an integral part of SQL. They offer certain features, and we can apply predefined operations to them. For example, we can perform calculations on values with the INTEGER data type, and we can apply operators such as + and – to them. However, the base data types of SQL are very elementary. Some users need much more complex and specialized data types. In an environment in which geographical data is stored, a data type as a two-dimensional (2D) coordinate, for example, would be very useful. Similarly, the data type color could be useful ...