anchor.diff:      | STDEV
       | STDEVP
       | SUM
  +	| TEXTIMAGE_ON
       | THROW
       | TIES
       | TIME
  
positive.code: // https://msdn.microsoft.com/en-us/library/ms188066.aspx
  table_constraint
      : (CONSTRAINT id)?
         ((PRIMARY KEY | UNIQUE) clustered? '(' column_name_list ')' index_options? (ON id)?
         | CHECK (NOT FOR REPLICATION)? '(' search_condition ')')
      ;
  
  
negative.code: // https://msdn.microsoft.com/en-us/library/ms190273.aspx
  alter_table
      : ALTER TABLE table_name (SET '(' LOCK_ESCALATION '=' (AUTO | TABLE | DISABLE) ')'
                               | ADD column_def_table_constraint
                               | DROP CONSTRAINT constraint=id
  							 | WITH CHECK ADD CONSTRAINT constraint=id FOREIGN KEY '(' fk = column_name_list ')' REFERENCES table_name '(' pk = column_name_list')'
  							 | CHECK CONSTRAINT constraint=id
  							 ) 
  							 ';'?
      ;
  
  // https://msdn.microsoft.com/en-us/library/ms174269.aspx
  