Abstract-The data rapidly increases with time. To deal massive data, or called big data, the idea of database as a service has been proposed. Outsourced database provider offers a lot of computing power and storage area. For organizations, they do not need to build their own infrastructure. It can reduce the cost of consumption. However, the data stored in the third-party provider side, if the third party can not be trusted, sensitive data within organization will have leaked crisis. In order to preserve privacy in organization's database, a number of approaches for preserving privacy have been proposed. Although the database has many security problems should be addressed, such as authentication, integrity, access control, and privacy. Also, studies on database need to consider performance efficiently when data updating. But there are huge problems so that we can not address easily. Hence, this paper mainly discusses the recently proposed approaches for preserving privacy only. We classify and organize approaches, and also discuss these. Approaches are divided into two categories, data encryption and data fragmentation. We introduce in simple common approach, give an illustration, and finally discuss challenges for each approach respectively. In the approach of data encryption, we introduce k-anonymity which is a mainstream solution. In data fragmentation, we introduce clustering which is new idea solution. Finally, we summarize these approaches for preserving privacy and discuss research future works.Index Terms-Preserving privacy, outsourced database, database security.