anchor.diff:      ;
   
   dropConstraintOption
  -    : (MAXDOP EQ_ NUMBER_ | ONLINE EQ_ (ON | OFF) | MOVE TO (schemaName LP_ columnName RP_ | ignoredIdentifier_ | STRING_))
  +    : (MAXDOP EQ_ NUMBER_ | ONLINE EQ_ onOffOption_ | MOVE TO (schemaName LP_ columnName RP_ | ignoredIdentifier_ | STRING_))
  +    ;
  +
  +onOffOption_
  +    : ON | OFF
       ;
   
   dropColumnSpecification
  
positive.code:     ;
  
  dataConsistencyCheckClause_
      : COMMA_? DATA_CONSISTENCY_CHECK EQ_ (ON | OFF)
      ;
  
  historyRetentionPeriodClause_
  
negative.code:     ;
  
  onHistoryTableClause
      : LP_ HISTORY_TABLE EQ_ tableName (COMMA_ DATA_CONSISTENCY_CHECK EQ_ onOffOption_)? RP_
      ;
  
  tableExistClause_
  