1. How many revisions of the standard have there been?
The SQL standard has gone through a number of revisions:
Year
Name
Alias
Comments
1986
SQL-86
SQL-87
First formalized by ANSI.
1989
SQL-89
FIPS127-1
Minor revision, in which the major addition were integrity constraints. Adopted as FIPS 127-1.
1992
SQL-92
SQL2, FIPS 127-2
Major revision (ISO 9075), Entry Level SQL-92 adopted as FIPS 127-2.
1999
SQL:1999
SQL3
Added regular expression matching, recursive queries (e.g. transitive closure), triggers, support for procedural and control-of-flow statements, non-scalar types, and some object-oriented features (e.g. structured types). Support for embedding SQL in Java (SQL/OLB) and vice-versa (SQL/JRT).
2003
SQL:2003
SQL 2003
Introduced XML-related features (SQL/XML), window functions, standardized sequences, and columns with auto-generated values (including identity-columns).
2006
SQL:2006
SQL 2006
ISO/IEC 9075-14:2006 defines ways in which SQL can be used in conjunction with XML. It defines ways of importing and storing XML data in an SQL database, manipulating it within the database and publishing both XML and conventional SQL-data in XML form. In addition, it enables applications to integrate into their SQL code the use of XQuery, the XML Query Language published by the World Wide Web Consortium (W3C), to concurrently access ordinary SQL-data and XML documents.[39]
2008
SQL:2008
SQL 2008
Legalizes ORDER BY outside cursor definitions. Adds INSTEAD OF triggers. Adds the TRUNCATE statement.[40]
2011
SQL:2011

A. What was added in the most recent one?
The most recent SQL standard came out late 2011. DDL features are one thing introduced into the newest SQL. It is used to improve the usability of generated and identity columns.
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