  Skyline and Ranking queries have gained great popularity in the recent years.
These two techniques are crucial for multi-criteria decision support
applications, which are now more popular than ever before. Skyline and Ranking
queries are, however, affected by well-known limitations. In the past recent
years, the database community provided numerous studies in this field with the
aim to overcome the weaknesses of these two approaches. This survey introduces
the reader to Skyline and Ranking queries, explaining the concepts on which
they are based, with the intent to present the compromise between the two
techniques: flexible skylines.
