SQL in a Nutshell

Categories of Syntax

SQL commands contains three main categories of syntax: identifiers, literals, and reserved and key words. Identifiers name objects that a user or a system process has created, such as a database, a table, the columns in a table, or a view. Literals are non-NULL values supplied to the system. Reserved and key words are words that have special meaning to the database SQL parser, such as SELECT, GRANT, DELETE, or CREATE.

Identifiers

Keep in mind that RDBMSs are built upon set theory: clusters contain sets of catalogs, catalogs contain sets of schemas, schemas contain sets of objects, and so on. At each level of this structure, each item requires a unique name or identifier.

This means that each object (whether a database, table, view, column, index, key, trigger, stored procedure, or constraint) in a RDBMS must be named. When issuing the command that creates a server object, a name for that new object must be specified.

There are two important sets of rules that experienced programmers keep in mind when choosing an identifier for a given item:

• The first set of rules include logical rules of thumb or conventions that ultimately create better database structures and data tracking. These are not so much required by SQL as they are the distilled experience of practiced programmers.

• The second set of rules are those set by the SQL standard and implemented by the vendors. The conventions for each vendor are covered later in this chapter.

Naming conventions

The naming conventions ...