Data uncertainty is pervasive in various fields

for example

economy

military

logistic

finance and telecommunication

etc.Uncertain data are inherent in some important applications

such as environmental surveillance

market analysis

Location-Based Service(LBS)

and quantitative economics research.Due to the importance of those applications and the rapidly increasing amount of uncertain data collected and accumulated

querying large collections of uncertain data has become an important task and has received more and more attention from the database community in recent years.This paper introduces the principle of uncertain data query

and surveys the advance of the research on uncertain data query processing

including Nearest Neighbor(NN)query

Reverse Nearest Neighbor(RNN)query

Ranking query

top-k query and join query.By a detailed comparison

the pros and cons of the techniques are discussed.In the end

the problems in current research and some future research issues are outlined.