12. The computer-implemented method of claim 11 , wherein the first, second, and third specified statistical view candidates comprise different statistical view candidates from the plurality of statistical view candidates, wherein refining the statistical view candidates further comprises at least one or more pruning techniques, wherein the one or more pruning techniques includes, in respective instances, each of: (i) merging statistical views that can be subsumed to form a new statistical view candidates; (ii) splitting a statistical view into two or more smaller statistical views; (iii) increasing the sampling rate on the statistical views; and (iv) removing constructs from a statistical view; wherein the set of refined statistical view candidates excludes at least four of the plurality of statistical view candidates, each statistical view candidate of which is excluded based on a respective, distinct one of the first, second, third, fourth, and fifth constraints, wherein no statistical view is generated based on the excluded at least four statistical view candidates, wherein the processing cost incurred in maintaining statistical views in the database management system is reduced by at least a measure associated with the excluded at least four statistical view candidates.
11. The computer-implemented method of claim 10 , wherein the plurality of distinct constraints include all of the first, second, third, fourth, and fifth constraints, whereby a processing cost incurred in statistical view maintenance by the query optimizer component of the database management system is reduced, relative to statistical view generation of the plurality of statistical view candidates not being restricted to the set of refined statistical view candidates, wherein the at least one generated statistical view, in respective instances, includes the column sub-expression and specifies to generate the statistics pertaining to the column group having the plurality of columns, wherein refining comprises, in respective instances, each of adding, deleting and updating at least one statistical view candidate; wherein the set of refined statistical view candidates excludes at least three of the plurality of statistical view candidates, each statistical view candidate of which is excluded based on a respective, distinct one of the first, second, third, fourth, and fifth constraints, wherein no statistical view is generated based on the excluded at least three statistical view candidates, wherein the processing cost incurred in maintaining statistical views in the database management system is reduced by at least a measure associated with the excluded at least three statistical view candidates.