Here is the XML schema for SQL-2003 (ISO/IEC 9075-2:2003 - Database Languages - SQL - Part 2: Foundation (SQL/Foundation)). Document about this XML schema in html format.
XML schema for other database SQL dialect such as Oracle, DB2, SQL Server, MySQL, Postgresql, Sybase, Teradata, Hive, Informix are working in progress as well. Feel free to contact us(info AT sqlparser.com) if you are interested in those XML schemas.
BNF Grammars for SQL-92, SQL-99 and SQL-2003. Prepared by: Jonathan Leffler.