Appendix B. SQL Reference

The Structured Query Language (SQL) is language that allows you to query, insert, and update data held in a relational database. The language has evolved during the past three decades to the latest incarnation of the language, which is called SQL99—otherwise known as SQL3. SQL99 is a standard published by the American National Standards Institute (ANSI) and ratified by the International Standards Organization (ISO). Today, SQL is the eminent language used by developers to work with relational databases.

Each provider of a Relational Database Management System (RDBMS) provides their own implementation of the language, but these implementations generally still comply with the standard. For example, the SQL statements, clauses, and functions you use with Oracle differ from those you use with MySQL, but both conform to the SQL standard. The good news is that you will find that each vendor's implementation conforms to the standard to such an extent that you do not have to learn a complete new set of commands to work with their product. However, you will have to refer to their documentation to discover which parts of SQL99 they adhere to and what vendor-specific extensions they have added to their product. In the process of using this book, you may have used one of any number of RDBMSs. So, rather than provide a reference to a specific vendor's implementation of the language, this appendix provides a reference to the most commonly used statements and clauses of the SQL99 standard. You should find that this reference, irrespective of the RDBMS you use, is generic enough to allow you to build the most commonly used SQL statements and execute them against your RDBMS with only a small number of changes to your code.