jodd-db/src/main/java/jodd/db/DbQuery.java
public Q setNull(final int index, final int type) {
		initPrepared();
		try {
			preparedStatement.setNull(index, type);
		} catch (SQLException sex) {
			throw new DbSqlException(this, "Failed to set null to parameter: " + index, sex);
		}
		return _this();
	}
public Q setNull(final int index, final int type) {
		initPrepared();
		try {
			preparedStatement.setNull(index, type);
		} catch (SQLException sex) {
			throw new DbSqlException(this, "Failed to set null to parameter: " + index, sex);
		}
		return _this();
	}
---------------------------------------------------------------- null