The existing works only consider how to efficiently process skyline computation for a single table.That is

they assume the issued skyline queries do not involve any traditional relational operator.Clearly

in most real applications

the query efficiency is extremely low because of this unreasonable assumption.Motivated by these facts

we regard skyline computation as a special relational operator and study the equivalence transformation rules of implementation order of it and traditional relational operators.Then based on these equivalence transformation rules

we can efficiently improve the query performance.Moreover

we present sufficient theoretical proofs to demonstrate the correctness of the proposed equivalence transformation rules.The extensive experiments also show that the after-transforming solutions markedly outperform the before-transforming counterparts.