The most important changes between SQL-89 and SQL-92, in my opinion, were modifications to the join syntax, specifically the addition of the OUTER JOIN clause.
SQL-99 really focused on the business analytics side of things, with additions such as Common Table Expressions and the SQL/PSM standard for defining Java-based modules. SQL/PSM (Persistent Stored Module) was actually added to SQL-92 in 1996, but is considered to be part of the SQL-99 standard.
Both SQL Server and Oracle do support parts of SQL-99 -– but neither of them supports the entire standard.
For more information on the ANSI SQL Standard, I recommend picking up a copy of A Guide to the SQL Standard (4th Edition) by C.J. Date and Hugh Darwen (Addison-Wesley Professional, 1996).
Do you have comments on this Ask the Expert Q&A? Let us know.
This was first published in May 2005