SQL Standards

The American National Standards Institute (http://www.ansi.org) first published a standard SQL specification in 1989. The ANSI SQL standard was later revised in 1992, and this is often referred to as SQL-92 or SQL-2. This was revised again, giving rise to the latest standard, known as SQL-99. Sometimes it is called SQL-3. Database vendors and third-party software companies have had varying levels of conformance to this standard. Most major database vendors support the SQL-92 standard. Generally what you find is that most vendors have their own extensions to the SQL language. Oracle is no exception in this matter. Nonetheless, Oracle has made efforts to maintain the ANSI standard. The reason for this is to provide an easier migration to third-party applications without a need to modify the SQL code. In Oracle 8 i , Oracle 9 i , and Oracle 10 g , Oracle has introduced a number of enhancements to conform to the SQL-99 standard. This appendix will review the main enhancements that you will see in this book. Examples will be given. It is important to realize that although many of these features are new to Oracle in version 9 i , these constructs have existed in other programming languages. For example, the CASE statement has been a part of MS SQL Server for some time and has been used in Cobol and C since their inception.