Recently, researches on relational database approaches to sensor networks are being tried. There occur, however, some problems in applying directly the traditional relational database concepts into a sensor network in that every database operation is performed only on the real existing data which are tuples in database relations. In addition, when searching tuples, it extracts only the tuples of which attribute values are exactly same with key values. These causes some problems to perform join operation in sensor networks. For instance, let us assume a sensor network that two different classes of nodes are randomly scattered in the same area. We cannot get join results to know the relationship between two different classes of sensing values because there might be no nodes at a exact same location. For a solution about the above described problem we propose in this paper new join operators its implementation method. This new join operators could provide more effective data management and standard interfaces to application programs in sensor networks. In addition, it would decrease energy consumption of nodes reducing the number of transmission.