从SQL-92到SQL：1999

SQL plays a very important role in the data base area,so its standardization attracts the at-tention of data base cooperation and the related standard organizations. Seven years later form the emer-gence of SQL-92,the SQL‘s new version SQL:1999 at last conies up at 1999. This paper describes themain contents of SQL: 1999 ,especially the changes to SQL-92 ,including the new added data types ,com-paring predicates ,semantics ,security ,trigger mechanism and other object relational characteristics,suchas user defined structured type ,stored procedure, function,method, typed relation and reference type.Some under developing parts and the future works are also described.