Wireless Sensor network has emerged as a promising technique that revolutionizes the way of sensing information. Dense deployed sensor nodes at a specific region are likely to transfer redundant data to the base station. This increase the communicational overhead and affects network lifetime. Since energy conservation is the key issue in WSNs, data aggregation should be incorporated in order to save energy. The main aim of data aggregation technique is to collect and aggregate data in an energy efficient manner so that network lifetime is enhanced. In this paper, we present a survey on data aggregation technique in Wireless Sensor Networks (WSN). Here, we explore different types of data aggregation algorithms based on network architecture, approaches and performance characteristics. Based on the study, the future research areas and issues to be focused are Security, Energy conservation, query processing, communication & uncertainty in sensor reading.