anchor.diff:      | alterColumn (SET | DROP) NOT NULL
       | alterColumn ADD GENERATED (ALWAYS | (BY DEFAULT)) AS IDENTITY (LP_ sequenceOptions RP_)?
       | alterColumn alterColumnSetOption alterColumnSetOption*
  -    | alterColumn DROP IDENTITY existClause_
  +    | alterColumn DROP IDENTITY columnExistClause_
       | alterColumn SET STATISTICS NUMBER_
       | alterColumn SET LP_ attributeOptions RP_
       | alterColumn RESET LP_ attributeOptions RP_
  
positive.code: newTableName
      : IDENTIFIER_
      ;
  
negative.code:     : ONLY?
      ;
  
  tableExistClause_
      : (IF EXISTS)?
      ;
  
  