SQL plays a very important rote in the data base area,so its standardization attracts the attention of data base cooperation and the related standard organizations. Seven years later form the emer gence of SQL-92,the SQLs new version SQL:t999 at last comes up at 1999. This paper describes the main 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,such as user defiaed structured type,stored procedure,function,method, typed relation and rets, fence type. Some under developing parts and the future works are also described.