HI,when i am uploading csv file in to custom object first it will check whether the data is existing r not in reseller__c object i.e based on the condition "Select Reseller_Region__c, Name, Id From Reseller__c where Reseller_category__c NOT IN('Distributor(T1)')'  "If the condition is satisfied  then it will update the records in Sales_Claim__c object.where i have to apply this condition in my code  i dont know .kindly let me know the solution asap.

apex:

public with sharing class uploadCSVcontroller {

        public String results   { get; set; }
        public Blob contentFile { get; set; }
        public String nameFile  { get; set; }
        public Integer rowCount { get; set; }
        public Integer colCount { get; set; }
 
        public pagereference Results() {
           
            List<List<String>> parsedCSV = new List<List<String>>();
           
          
           
            //Reseller__c Res = [Select Reseller_Region__c, Name, Id From Reseller__c where Reseller_category__c NOT IN('Distributor(T1)')];                 
            //System.debug('Res:'+Res);
           
          
            rowCount = 0;
            colCount = 0;
            if (contentFile != null){
                String fileString = contentFile.toString();
                parsedCSV = parseCSV(fileString, false);
               
                 rowCount = parsedCSV.size();
                System.debug('RowCount:'+rowCount);
               
                List<Sales_Claim__c> recs=new List<Sales_Claim__c>();
                //System.debug('RECS:'+recs);
              
                Integer rowCount=0;
               
               
               
                 for (List<String> row : parsedCSV)
                  {
                   Sales_Claim__c rec=new  Sales_Claim__c();
                  
                   recs.add(rec);
                   System.debug('recs1:'+recs);
                   for (String col : row)
                   {
                     rec.put('Reseller__c', row[0]);
                     rec.put('Quarter__c', row[1]);
                     System.debug('QA:'+row[1]);
                    
                     rec.put('Status__c', row[2]);
                    }
                   
                   }
                    
                     insert recs;
                     ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.FATAL, 'Successfully Uploaded' );
                     ApexPages.addMessage(myMsg);
                     //System.debug('Successfull Inserted:'+recs);
  
            }
            return null;
        }

      
        public static List<List<String>> parseCSV(String contents,Boolean skipHeaders) {
            List<List<String>> allFields = new List<List<String>>();
            contents = contents.replaceAll(',"""',',"DBLQT').replaceall('""",','DBLQT",');
            //System.debug('contents:'+contents);
            contents = contents.replaceAll('""','DBLQT');
            System.debug('contents:'+contents);
            List<String> lines = new List<String>();
            try {
              
                lines = contents.split('\r'); // using carriage return accomodates windows, unix, and mac files
             
            } catch (System.ListException e) {
                System.debug('Limits exceeded?' + e.getMessage());
            }
            Integer num = 0;
            for(String line: lines) {
                // check for blank CSV lines (only commas)
                if (line.replaceAll(',','').trim().length() == 0) break;
              
                List<String> fields = line.split(',');
                List<String> cleanFields = new List<String>();
                String compositeField;
                Boolean makeCompositeField = false;
                for(String field: fields) {
                    if (field.startsWith('"') && field.endsWith('"')) {
                        cleanFields.add(field.replaceAll('DBLQT','"'));
                    } else if (field.startsWith('"')) {
                        makeCompositeField = true;
                        compositeField = field;
                    } else if (field.endsWith('"')) {
                        compositeField += ',' + field;
                        cleanFields.add(compositeField.replaceAll('DBLQT','"'));
                        makeCompositeField = false;
                    } else if (makeCompositeField) {
                        compositeField +=  ',' + field;
                    } else {
                        cleanFields.add(field.replaceAll('DBLQT','"'));
                    }
                }
              
                allFields.add(cleanFields);
            }
            if (skipHeaders) allFields.remove(0);
            System.debug('allFields:'+allFields);
            return allFields;
                
        }

    }

Vpage:

<apex:page controller="uploadCSVcontroller" >
<apex:pageBlock >
 <apex:message />
      <apex:form >
      <apex:inputFile value="{!contentFile}" filename="{!nameFile}" /><br/>
      <apex:commandButton value="Upload" action="{!Results}" id="theButton"/>
      </apex:form>
    </apex:pageBlock>
      <apex:outputPanel id="results">
      <p>Filename: {!nameFile}</p>
      <p>TotalRecords: {!rowCount}</p>
     
        <table title="CSV Output" border="1" width="100%">
           <apex:repeat value="{!results}" var="row">
               <tr>
                   <apex:repeat value="{!row}" var="cell">
                       <td> {!cell} </td>
                   </apex:repeat>
               </tr>
           </apex:repeat>
         </table>
      </apex:outputPanel>
     
      </apex:page>