public String returnInsertColumnsName() {
		StringBuilder sb = new StringBuilder();

		List<String> list = columnMap.get(this.getClass());
		int i = 0;
		for (String column : list) {
			if (isNull(column))
				continue;

			if (i++ != 0)
				sb.append(',');
			sb.append(column);
		}
		return sb.toString();
	}