Apex SOQL only Createable Fields

gistfile1.txt

List<Schema.SObjectField> flds = Schema.sObjectType.Lead.fields.getmap().values();

List<String> selectFields = new List<String>();

for (Schema.SObjectField fld : flds) {
  Schema.DescribeFieldResult fldDesc = fld.getDescribe();
  if (fldDesc.isCreateable() == true) {
    selectFields.add(fldDesc.getName());
  }
}

String soql = 'SELECT ' + String.join(selectFields, ',') + ' FROM Lead';
system.debug(soql);