31 Oct Sql server tutorial 02 Working with the SQL Environment
- Key Skills & Concepts
- Understand the SQL Environment
- Understand SQL Catalogs
- Name Objects in an SQL Environment
- Create a Schema
- Create a Database
In Chapter 1, I discuss relational theory, SQL, and relational database management
systems (RDBMSs). In this chapter, I want to take this discussion one step further and
introduce you to the SQL environment as it is defined in the SQL standard. The SQL
environment provides the structure in which SQL is implemented. Within this structure,
you can use SQL statements to define database objects and store data in those objects.
However, before you start writing SQL statements, you should have a basic understanding
of the foundations on which the SQL environment is built so you can apply this
information throughout the rest of the book. In fact, you might find it helpful to refer back
to this chapter often to help gain a conceptual understanding of the SQL environment and
how it relates to the SQL elements you’ll learn about in subsequent chapters.
Understand the SQL Environment
The SQL environment is, quite simply, the sum of all the parts that make up that
environment. Each distinct part, or component, works in conjunction with other
components to support SQL operations such as creating and modifying objects, storing
and querying data, or modifying and deleting that data. Taken together, these components
form a model on which an RDBMS can be based. This does not imply, however, that
RDBMS vendors adhere strictly to this model; which components they implement and
how they implement them are left, for the most part, to the discretion of those vendors.
Even so, I want to provide you with an overview of the way in which the SQL
environment is defined in terms of its distinct components as they are described in the
The SQL environment is made up of six types of components, as shown in Figure 2-1.
The SQL client and SQL servers are part of the SQL implementation and are therefore
subtypes of that component.
Figure 2-1 The components of the SQL environment
Notice that there is only one SQL agent and one SQL implementation, but there are
multiple components for other types, such as catalogs and sites. According to SQL, there
must be exactly one SQL agent and SQL implementation and zero or more SQL client
modules, authorization identifiers, and catalogs. The standard does not specify how many
sites are supported, but implies multiple sites.
Each type of component performs a specific function within the SQL environment.