SQL Bible [Electronic resources] نسخه متنی

Summary

While it may not be apparent at the first
look, the data types are there to safeguard us and make our life easier. This
chapter describes and categorizes all existing data types (character and binary
strings, precise and approximate numbers, dates and time, user-defined and
object types, as well as few others that don't fit well any of the above) and
analyzes variations between vendor implementations and SQL99 standards.

It is very important to know what data
types are available in each implementation and to understand the correspondence
between them and SQL99 standards.

You also need to consider ramifications of
using a particular data type to store a particular kind of data.

Each of the three RDBMS vendors discussed
in this book has its own proprietary extensions — in addition to SQL99 standard
mandated data types.

The concept of
NULL is introduced in this chapter. While
not defining a data type, this concept is crucial for understanding how data is
created, retrieved, and compared.