Visual C++ 6 Unleashed

Visual C++ 6 Unleashed

By MICKEY WILLIAMS and David Bennett

Structured Query Language

SQL (Structured Query Language) is a common language found in almost all databases. SQL is a relatively simple language, yet it is powerful enough to perform almost any operations you would need to do with a database. SQL was designed to give developers a common method for updating and retrieving data from tables on a database. SQL allows you to access your database from Visual C++ through OLE DB or ODBC. There are many concepts and commands common to most SQL implementations and the most commonly used SQL commands are standard across databases.

All the database interfaces in the next four chapters allow you to use SQL within the framework of the database interface, so let's take a quick look at the basics of the SQL language. This section looks at a generic version of the SQL grammar, which can be used with OLE DB, ODBC, and the other interfaces you will be working with.

CAUTION

Note that almost every database provides its own dialect of SQL that can use slightly different syntax or support a slightly different set of features, so the grammar that you see here might not work with the query tools provided by your favorite database.

Most databases are highly compliant with the ANSI SQL standard, but some may fall short of full compliance. If you run into problems, check out your database's documentation to see how your database implements its SQL command syntax.

The following sections look at the three basic groups of SQL statements. Data Definition Language (DDL) is used to set up the structure of the database, and Data Control Language (DCL) is used to work with user permissions for certain objects. Finally, and most importantly, Data Manipulation Language (DML) is used to do everything else, including adding and modifying data as well as performing queries. These languages are all a part of SQL and aren't really separate languages, although most applications will use only statements from one of the three available groups.

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