anchor.diff:  validation_clauses
       : VALIDATE REF UPDATE (SET DANGLING TO NULL)?
       | VALIDATE STRUCTURE 
  -        ( CASCADE  FAST
  +        ( CASCADE FAST
           | CASCADE online_or_offline? into_clause?
           | CASCADE
           )?
  
positive.code: // https://docs.oracle.com/database/121/SQLRF/statements_4008.htm#SQLRF56110
  unified_auditing
      : {version12}? 
        AUDIT (POLICY policy_name ((BY|EXCEPT) (','? audit_user)+ )? 
                                  (WHENEVER NOT? SUCCESSFUL)?
              | CONTEXT NAMESPACE oracle_namespace 
                        ATTRIBUTES (','? attribute_name)+ (BY (','? audit_user)+)?
  
negative.code: //https://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_4006.htm#SQLRF01106
  associate_statistics
      : ASSOCIATE STATISTICS 
          WITH (column_association | function_association)
          storage_table_clause?
        ';'
      ;
  
  