Data integration plays a very important role in data management and analytical area. Although there have been decades since the data integration problem was first proposed, there are many data integration problems that remain unsolved. This study surveys the works in data integration area from 2001 until now. By categorizing these papers and their methodologies, it is able to summarize how these works develop and how their research topics shift from time to time. Several research topics are also filtered out that draw much attention recently and hopefully the survey and conclusions may provide guidance to the related researchers.