anchor.diff:  
   // https://msdn.microsoft.com/en-us/library/ms190273.aspx
   alter_table
  -    : ALTER TABLE table_name SET '(' LOCK_ESCALATION '=' (AUTO | TABLE | DISABLE) ')' ';'?
  -    | ALTER TABLE table_name ADD column_def_table_constraint ';'?
  +    : ALTER TABLE table_name (SET '(' LOCK_ESCALATION '=' (AUTO | TABLE | DISABLE) ')'
  +                             | ADD column_def_table_constraint) ';'?
       ;
   
   // https://msdn.microsoft.com/en-us/library/ms174269.aspx
  
positive.code:     ;
  
  fetch_cursor
      : FETCH ((NEXT | PRIOR | FIRST | LAST | ABSOLUTE expression | RELATIVE expression)? FROM)?
        GLOBAL? cursor_name (INTO LOCAL_ID (',' LOCAL_ID)*)? ';'?
      ;
  
  // https://msdn.microsoft.com/en-us/library/ms190356.aspx
  // Runtime check.
  set_special
      : SET id (id | constant | LOCAL_ID | on_off) ';'?
      // https://msdn.microsoft.com/en-us/library/ms173763.aspx
      | SET TRANSACTION ISOLATION LEVEL
        (READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SNAPSHOT | SERIALIZABLE) ';'?
      // https://msdn.microsoft.com/en-us/library/ms188059.aspx
      | SET IDENTITY_INSERT table_name on_off ';'?
      ;
  
  // Expression.
  
negative.code: // Labels for better AST traverse.
  cfl_statement
      // https://msdn.microsoft.com/en-us/library/ms190487.aspx
      : BEGIN ';'? sql_clauses? END ';'?               #block_statement
      // https://msdn.microsoft.com/en-us/library/ms181271.aspx
      | BREAK ';'?                                     #break_statement
      // https://msdn.microsoft.com/en-us/library/ms174366.aspx
  