“…In addition, selectivity estimation has been shown to be useful in many other areas of database processing, e.g., top-k query processing, skyline query processing, load-balancing in parallel join query execution, and spatio-temporal query processing [3,6,21,22,26,27]. Motivated by such applications, there has been a great deal of work on the problem of selectivity estimation such as histograms [1,2,8,11,12,19,24,28], wavelet transformation [18,29], SVD [23], discrete cosine transform [17], and sampling [13]. Among these approaches, histograms have been shown to be one of the most popular and effective ways to obtain accurate estimates of selectivity for multi-dimensional queries [8].…”