Export CSV File data by using Apex Code

 List<company__c> extractcompanyMemList = new List<company__c>();

List<company__c> companytList = [select id,name,(select id from companymemebers__r) from company__c];

for(RequestClaimJunction__c company: companytList){
	List<companymemeber__c> companyMemList = company.companymemebers__r;
	if(companyMemList.size() == 0) {
		extractcompanyMemList.add(company);
	}
}

String generatedCSVFile ='';
List<String> queryFields = new List<String>{'Id','Partner Account','Status'};
String fileRow = '';

for(company__c company: extractcompanyMemList){
	fileRow = '';
	fileRow = fileRow +','+ company.Id;
	fileRow = fileRow +','+ company.Name;
	fileRow = fileRow.replaceFirst(',','');
	generatedCSVFile = generatedCSVFile + fileRow + '\n';
}

Messaging.EmailFileAttachment csvAttachment = new Messaging.EmailFileAttachment();
Blob csvBlob = blob.valueOf(generatedCSVFile);
String csvName = 'company details which doesn't have members.csv';
csvAttachment.setFileName(csvName);
csvAttachment.setBody(csvBlob);
Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
String[] toAddresses = new String[]{'Your Email Id'};
String subject = 'company details which doesn't have members CSV';
email.setSubject(subject);
email.setToAddresses(toAddresses);
email.setPlainTextBody('company details which doesn't have members CSV');
email.setFileAttachments(new Messaging.EmailFileAttachment[]{csvAttachment});
Messaging.SendEmailResult[] r = Messaging.sendEmail(new Messaging.SingleEmailMessage[]{email});