code: private StringBuilder onRelationColumns(String columnNames, String columnValues, StringBuilder columnNameBuilder,
          StringBuilder columnValueBuilder, RelationHolder rl) {
          int relnameIndx = columnNameBuilder.indexOf("\"" + rl.getRelationName() + "\"");
          if (relnameIndx != -1 && rl.getRelationValue() != null) {
  
              List<String> cNameArray = Arrays.asList(columnNames.split(","));
              List<String> cValueArray = new ArrayList<String>(Arrays.asList(columnValues.split(",")));
              int cValueIndex = cNameArray.indexOf("\"" + rl.getRelationName() + "\"");
  
              if (cValueArray.get(cValueIndex).equals("null")) {
                  columnNameBuilder.delete(relnameIndx - 1, relnameIndx + rl.getRelationName().length() + 2);
                  cValueArray.remove(cValueIndex);
                  columnValueBuilder =
                      new StringBuilder(cValueArray.toString().substring(1, cValueArray.toString().length() - 1));
  
              }
  
          }
          return columnValueBuilder;
      }
docs: On relation columns.
  
  @param columnNames
  the column names
  @param columnValues
  the column values
  @param columnNameBuilder
  the column name builder
  @param columnValueBuilder
  the column value builder
  @param rl
  the rl
  @return To remove redundant columns in insert query