title: SQLError:Can't DROP Index_name; check that column/key exists -- occurs multiple times
body: <p>I want to execute a alter command on a table, create table and alter table commands are as below.</p>
  
  <pre><code>CREATE TABLE `xyz` (
        `entity_id` int(11) NOT NULL AUTO_INCREMENT,
        `masterform_id` int(11) NOT NULL DEFAULT '1',
        `app_status` varchar(500) DEFAULT NULL,
        `NegativeMarks` decimal(15,5) DEFAULT NULL,
        `ActualScore` decimal(15,5) DEFAULT NULL,
        `RawScore` decimal(15,5) DEFAULT NULL,
        `PANProratedMarks` decimal(15,5) DEFAULT NULL,
        `PANNormalizedMarks` decimal(15,5) DEFAULT NULL,
        `RRBZoneNormalizedMarks` decimal(15,5) DEFAULT NULL,
        `RRBZoneProratedMarks` decimal(15,5) DEFAULT NULL,  
        `RRBZoneAllocationTempStorage` varchar(200) DEFAULT NULL,
        `GraduatePercentage` decimal(15,5) DEFAULT NULL,
          `PANAllocationTempStorage` varchar(1500) DEFAULT NULL,
        PRIMARY KEY (`entity_id`),
        UNIQUE KEY `app_seq_no` (`app_seq_no`),
        UNIQUE KEY `ParticipantID` (`ParticipantID`),
        UNIQUE KEY `RegistrationNo` (`RegistrationNo`),  
        KEY `idx_PANNormalizedMarks` (`PANNormalizedMarks`),  
        KEY `idx_RRBZoneNormalizedMarks` (`RRBZoneNormalizedMarks`)
      ) ENGINE=InnoDB AUTO_INCREMENT=273252 DEFAULT CHARSET=latin1 ROW_FORMAT=DYNAMIC
  
  
  Alter table xyz
      modify column ActualScore decimal(15,5),
      modify column app_status varchar(500),
      add index CalculatedCategory(CalculatedCategory),
      modify column GraduatePercentage decimal(15,5),
      modify column NegativeMarks decimal(15,5),
      modify column PANAllocationTempStorage varchar(1500),
      modify column PANNormalizedMarks decimal(15,5),
      modify column PANProratedMarks decimal(15,5),
      drop index idx_ParticipantID,
      add unique ParticipantID(ParticipantID),
      modify column RawScore decimal(15,5),
      drop index idx_RegistrationNo,
      add unique RegistrationNo(RegistrationNo),
      modify column RRBZoneNormalizedMarks decimal(15,5),
      modify column RRBZoneProratedMarks decimal(15,5);
  </code></pre>
  
  <p>I am getting this error:</p>
  
  <pre><code>SQLError:Can't DROP 'idx_ParticipantID'; check that column/key exists
  </code></pre>
  
  <p>But I am getting this same 104 times. Could you please let me know why am I getting this error 104 times in log? If the index doesnt exist it should just give the error once, please correct me if I am wrong.</p>